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Scientific American Supplement No. 415
NEW YORK, DECEMBER 15, 1883
Scientific American Supplement. Vol. XVI, No. 415.
Scientific American established 1845
Scientific American Supplement, $5 a year.
Scientific American and Supplement, $7 a year.
TABLE OF CONTENTS.
I. CHEMISTRY AND METALLURGY.—Carbon in Steel.
Heat developed in Forging.
Recent Studies on the Constitution of Alkaloids.—Extract from a lecture delivered before the Philadelphia College of Pharmacy. —By SAML.P. SADTLER.
II. ENGINEERING AND MECHANICS.—Apparatus for Extracting Starch from Potatoes.—With engraving.
A Simple Apparatus for describing Ellipses.—By Prof. E.J. HALLOCK. 1 figure.
A Novel Propeller Engine.—With full description and numerous engravings.—By Prof. MACCORD.
The New Russian Torpedo Boat, the Poti.—With engraving.
A New Steamer Propelled by Hydraulic Reaction—Figures showing plan and side views of the steamer.
A New Form of Flexible Band Dynamometer.—By Prof. W.C. UNWIN. 4 figures.
III. TECHNOLOGY.—Enlarging on Argentic Paper and Opals.—By A. GOODALL.
The Manufacture and Characteristics of Photographic Lenses.
Improved Developers for Gelatine Plates.—By DR. EDER.
The Preparation of Lard for Use in Pharmacy.—By Prof. REDWOOD.
Anti-Corrosion Paint.
Manufacture of Charcoal in Kilns.—Different kilns used.
IV. ART, ARCHITECTURE, AND ARCHAEOLOGY.—The German National Monument.—With two engravings of the statues of Peace and War.
The Art Aspects of Modern Dress.
Artisans' Dwellings, Hornsey, London.—With engraving.
Discovery of Ancient Church In Jerusalem.
V. ELECTRICITY, HEAT. ETC.—See's Gas Stove.—With engraving.
Rectification of Alcohol by Electricity. 3 engravings showing Apparatus for Hydrogenizing Impure Spirits. Electrolyzing Apparatus, and Arrangement of the Siemens Machine.
VI. GEOLOGY.—On the Mineralogical Localities in and around New York City.—By NELSON H. DARTON.
VII. NATURAL HISTORY.—The Zoological Society's Gardens, London.—With full page engravings showing the new Reptile House, and the Babiroussa family.
VIII. HORTICULTURE.—The Kauri Pine—Damarra Australis.— With engraving.
How to Successfully Transplant Trees.
IX. MEDICINE, HYGIENE, ETC.—On the Treatment of Congestive Headache.—By Dr. J.L. CORNING.
The Use of the Mullein Plant in the Treatment of Pulmonary Consumption.—By Dr. J.B. QUINLAN.
Action of Mineral Waters and of Hot Water upon the Bile.
Vivisection.—Apparatus Used.—Full page of engravings.
Insanity from Alcohol.—Intemperance a fruitful as well as inexhaustible source for the increase of insanity.—By Dr. A. BAER, Berlin.
Plantain as a Styptic.—By J.W. COLCORD.
Danger from Flies.
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THE GERMAN NATIONAL MONUMENT.—WAR AND PEACE.
In our SUPPLEMENT No. 412 we gave several engravings and a full description of the colossal German National monument "Germania," lately unveiled on the Niederwald slope of the Rhine. We now present, as beautiful suggestions in art, engravings of the two statues, War and Peace, which adorn the corners of the monumental facade. These figures are about twenty feet high. The statue of War represents an allegorical character, partly Mercury, partly mediaeval knight, with trumpet in one hand, sword in the other. The statue of Peace represents a mild and modest maiden, holding out an olive branch in one hand and the full horn of peaceful blessings in the other. Between the two statues is a magnificent group in relief representing the "Watch on the Rhine." Here the Emperor William appears in the center, on horseback, surrounded by a noble group of kings, princes, knights, warriors, commanders, and statesmen, who, by word or deed or counsel, helped to found the empire—an Elgin marble, so to speak, of the German nation.
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A writer in the London Lancet ridicules a habit of being in great haste and terribly pressed for time which is common among all classes of commercial men, and argues that in most cases there is not the least cause for it, and that it is done to convey a notion of the tremendous volume of business which almost overwhelms the house. The writer further says that, when developed into a confirmed habit, it is fertile in provoking nervous maladies.
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THE ART ASPECTS OF MODERN DRESS.
At a recent conversazione of the London Literary and Artistic Society, Mr. Sellon read a paper upon this subject. Having expressed his belief that mere considerations of health would never dethrone fashion, the lecturer said he should endeavor to show on art principles how those who were open to conviction could have all the variety Fashion promised, together with far greater elegance than that goddess could bestow, while health received the fullest attention. Two excellent societies, worthy of encouragement up to a certain point, had been showing us the folly and wickedness of fashionable dress—dress which deformed the body, crippled the feet, confined the waist, exposed the chest, loaded the limbs, and even enslaved the understanding. But these societies had been more successful in pulling down than in building up, and blinded with excess of zeal were hurrying us onward to a goal which might or might not be the acme of sanitative dress, but was certainly the zero of artistic excellence. The cause of this was not far to seek. We were inventing a new science, that of dress, and were without rules to guide us. So long as ladies had to choose between Paris fashions and those of Piccadilly Hall, they would, he felt sure, choose the former. Let it be shown that the substitute was both sanitary and beautiful, capable of an infinite variety in color and in form—in colors and forms which never violated art principle, and in which the wearer, and not some Paris liner, could exercise her taste, and the day would have been gained. This was the task he had set himself to formulate, and so doing he should divide his subject in two—Color and Form.
In color it was desirable to distinguish carefully between the meaning of shade, tint, and hue. It was amazing that a cultured nation like the English should be so generally ignorant of the laws of color harmony. We were nicely critical of music, yet in color were constantly committing the gravest solecisms. He did not think there were seventeen interiors in London that the educated eye could wander over without pain. Yet what knowledge was so useful? We were not competent to buy a picture, choose a dress, or furnish a house without a knowledge of color harmony, to say nothing of the facility such knowledge gave in all kinds of painting on porcelain, art needlework, and a hundred occupations.
An important consideration in choosing colors for dress was the effect they would have in juxtaposition. Primary colors should be worn in dark shades; dark red and dark yellow, or as it was commonly called, olive green, went well together; but a dress of full red or yellow would be painful to behold. The rule for full primaries was, employ them sparingly, and contrast them only with black or gray. He might notice in passing that when people dressed in gray or black the entire dress was usually of the one color unrelieved. Yet here they had a background that would lend beauty to any color placed upon it.
Another safe rule was never to place together colors differing widely in hue. The eye experienced a difficulty in accommodating itself to sudden changes, and a species of color discord was the consequence. But if the colors, even though primaries, were of some very dark or very light shade, they become harmonious. All very dark shades of color went well with black and with each other, and all very light shades went well with white and each other.
A much-vexed question with ladies was, "What will suit my complexion?" The generally received opinion was that the complexion was pink, either light or dark, and colors were chosen accordingly, working dire confusion. But no one living ever had a pink complexion unless a painted one. The dolls in the Lowther Arcade were pink, and their pink dresses were in harmony. No natural complexion whatever was improved by pink; but gray would go with any. The tendency of gray was to give prominence to the dominant hue in the complexion. When an artist wished to produce flesh color he mixed white, light red, yellow ocher, and terra vert. The skin of a fair person was a gray light red, tinged with green; the color that would brighten and intensify it most was a gray light sea green, tinged with pink—in other words, its complementary. A color always subtracted any similar color that might exist in combination near it. Thus red beside orange altered it to yellow; blue beside pink altered it to cerise. Hence, if a person was so unfortunate as to have a muddy complexion, the worst color they could wear would be their own complexion's complementary—the best would be mud color, for it would clear their complexion.
Passing on to the consideration of form in costume, the lecturer urged that the proper function of dress was to drape the human figure without disguising or burlesquing it. An illustration of Miss Mary Anderson, attired in a Greek dress as Parthenia, was exhibited, and the lecturer observed that while the dress once worn by Greek women was unequaled for elegance, Greek women were not in the habit of tying their skirts in knots round the knees, and the nervous pose of the toes suggested a more habitual acquaintance with shoes and stockings.
An enlargement from a drawing by Walter Crane was shown as illustrating the principles of artistic and natural costume—costume which permitted the waist to be the normal size, and allowed the drapery to fall in natural folds—costume which knew nothing of pleats and flounces, stays and "improvers"—costume which was very symbolization and embodiment of womanly grace and modesty.
A life-sized enlargement of a fashion plate from Myra's Journal, dated June 1, 1882, was next shown. The circumference of the waist was but 123/4 in., involving an utter exclusion of the liver from that part of the organization, and the attitude was worthy of a costume which was the ne plus ultra of formal ugliness.
Having shown another and equally unbecoming costume, selected from a recent issue by an Oxford Street firm, the lecturer asked, Why did women think small waists beautiful? Was it because big-waisted women were so frequently fat and forty, old and ugly? A young girl had no waist, and did not need stays. As the figure matured the hips developed, and it was this development which formed the waist. The slightest artificial compression of the waist destroyed the line of beauty. Therefore, the grown woman should never wear stays, and, since they tended to weaken the muscles of the back, the aged and weak should not adopt them. A waist really too large was less ungraceful than a waist too small. Dress was designed partly for warmth and partly for adornment. As the uses were distinct, the garments should be so. A close-fitting inner garment should supply all requisite warmth, and the outer dress should be as thin as possible, that it might drape itself into natural folds. Velvet, from its texture, was ill adapted for this. When worn, it should be in close fitting garments, and in dark colors only. It was most effective when black.
Turning for a few moments, in conclusion, to men's attire, the lecturer suggested that the ill-success of dress reformers hitherto had been the too-radical changes they sought to introduce. We could be artistic without being archaic. Most men were satisfied without clothes fairly in fashion, a tolerable fit, and any unobtrusive color their tailor pleased. He would suggest that any reformation should begin with color.
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ARTISANS' DWELLINGS, HORNSEY.
The erection of artisans' dwellings is certainly a prominent feature in the progress of building in the metropolis, and speculative builders who work on a smaller scale would do well not to ignore the fact. The Artisans, Laborers, and General Dwellings Company (Limited) has been conspicuously successful in rearing large blocks of dwellings for artisans, clerks, and others whose means necessitates the renting of a convenient house at as low a rental as it is possible to find it. We give an illustration of a terrace of first-class houses built by the above company, who deserve great praise for the spirited and liberal manner in which they are going to work on this the third of their London estates—the Noel Park Estate, at Hornsey. On the estates at Shaftesbury and Queen's Parks they have already built about three thousand houses, employing therein a capital of considerably over a million sterling, while at Noel Park they are rapidly covering an estate of one hundred acres, which will contain, when completed, no less than two thousand six hundred houses, to be let at weekly rentals varying from 6s. to 11s. 6d., rates and taxes all included. The object has been to provide separate cottages, each in itself complete, and in so doing they have not made any marked departure from the ordinary type of suburban terrace plan, but adopting this as most favorable to economy, have added many improvements, including sanitary appliances of the latest and most approved type.
The most important entrance to Noel Park is by Gladstone Avenue, a road 60 ft. wide leading from the Green Lanes to the center of the estate. On either side of this road the houses are set back 15 ft., in front of which, along the edge of the pavement, trees of a suitable growth are being planted, as also on all other roads on the estate. About the center of Gladstone Avenue an oval space has been reserved as a site for a church, and a space of five acres in another portion of the estate has been set apart to be laid out as a recreation ground, should the development of the estate warrant such an outlay. The remaining streets are from 40 ft. to 50 ft. in width, clear of the garden space in front of the houses. Shops will be erected as may be required.
The drainage of the estate has been arranged on the dual system, the surface water being kept separate from the sewage drains. Nowhere have these drains been carried through the houses, but they are taken directly into drains at the back, having specially ventilated manholes and being brought through at the ends of terraces into the road sewers; the ventilating openings in the roads have been converted into inlet ventilators by placing upcast shafts at short intervals, discharging above the houses. This system of ventilation was adopted on the recommendation of Mr. W.A. De Pape, the engineer and surveyor to the Tottenham Local Board.
All the houses are constructed with a layer of concrete over the whole area of the site, and a portion of the garden at back. Every room is specially ventilated, and all party walls are hollow in order to prevent the passage of sound. A constant water supply is laid on, there being no cisterns but those to the water-waste preventers to closets. All water pipes discharge over open trapped gullies outside.
The materials used are red and yellow bricks, with terracotta sills, the roofs being slated over the greater part, and for the purpose of forming an agreeable relief, the end houses, and in some cases the central houses, have red tile roofs, the roofs over porches being similarly treated. The houses are simply but effectively designed, and the general appearance of the finished portion of the estate is bright and cheerful. All end houses of terraces have been specially treated, and in some cases having rather more accommodation than houses immediately adjoining, a slightly increased rental is required. There are five different classes of houses. The first class houses (which we illustrate this week) are built on plats having 16 ft. frontage by 85 ft. depth, and containing eight rooms, consisting of two sitting rooms, kitchen, scullery, with washing copper, coal cellar, larder, and water-closet on ground floor, and four bedrooms over. The water-closet is entered from the outside, but in many first-class houses another water-closet has been provided on the first floor, and one room on this floor is provided with a small range, so that if two families live in the one house they will be entirely separated. The rental of these houses is about 11s. to 11s. 6d. per week. Mr. Rowland Plumbe, F.R.I.B.A., of 13 Fitzroy Square, W., is the architect.—Building and Engineering Times.
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ENLARGING ON ARGENTIC PAPER AND OPALS.
By A. GOODALL.
[Footnote: Read before the Dundee and East of Scotland Photographic Association.]
The process of making gelatino bromide of silver prints or enlargements on paper or opal has been before the public for two or three years now, and cannot be called new; but still it is neither so well known nor understood as such a facile and easy process deserves to be, and I may just say here that after a pretty extensive experience in the working of it I believe there is no other enlarging process capable of giving better results than can be got by this process when properly understood and wrought, as the results that can be got by it are certainly equal to those obtainable by any other method, while the ease and rapidity with which enlarged pictures can be made by it place it decidedly ahead of any other method. I propose to show you how I make a gelatino bromide enlargement on opal.
[Mr. Goodall then proceeded to make an enlargement on a 12 by 10 opal, using a sciopticon burning paraffin; after an exposure for two and a-half minutes the developer was applied, and a brilliant opal was the result.]
We now come to the paper process, and most effective enlargements can be made by it also; indeed, as a basis for coloring, nothing could well be better. Artists all over the country have told me that after a few trials they prefer it to anything else, while excellent and effective plain enlargements are easily made by it if only carefully handled. A very good enlargement is made by vignetting the picture, as I have just done, with the opal, and then squeezing it down on a clean glass, and afterward framing it with another glass in front, when it will have the appearance almost equal to an opal. To make sure of the picture adhering to the glass, however, and at the same time to give greater brilliancy, it is better to flow the glass with a 10 or 15 grain solution of clear gelatine before squeezing it down. The one fault or shortcoming of the plain argentic paper is the dullness of the surface when dry, and this certainly makes it unsuitable for small work, such as the rapid production of cartes or proofs from negatives wanted in a hurry; the tone of an argentic print is also spoken of sometimes as being objectionable; but my impression is, that it is not so much the tone as the want of brilliancy that is the fault there, and if once the public were accustomed to the tones of argentine paper, they might possibly like them twice as well as the purples and browns with which they are familiar, provided they had the depth and gloss of a silver print; and some time ago, acting on a suggestion made by the editor of the Photographic News, I set about trying to produce this result by enameling the paper with a barium emulsion previous to coating it with the gelatinous bromide of silver. My experiments were successful, and we now prepare an enamel argentic paper on which the prints stand out with brilliancy equal to those on albumenized paper. I here show you specimens of boudoirs and panels—pictures enlarged from C.D.V.—negatives on this enamel argentic.
[Mr. Goodall then passed round several enlargements from landscape and portrait negatives, which it would have been difficult to distinguish from prints on double albumenized paper.]
I have already spoken of the great ease and facility with which an argentic enlargement may be made as compared with a collodion transfer, for instance; but there is another and more important point to be considered between the two, and that is, their durability and permanence. Now with regard to a collodion transfer, unless most particular care be taken in the washing of it (and those who have made them will well know what a delicate, not to say difficult, job it is to get them thoroughly freed from the hypo, and at the same time preserve the film intact), there is no permanence in a collodion transfer, and that practically in nine cases out of ten they have the elements of decay in them from the first day of their existence. I know, at least in Glasgow, where an enormous business has been done within the last few years by certain firms in the club picture trade (the club picture being a collodion transfer tinted in oil or varnish colors), there are literally thousands of pictures for which thirty shillings or more has been paid, and of which the bare frame is all that remains at the present day; the gilt of the frames has vanished, and the picture in disgust, perhaps, has followed it. In short, I believe a collodion transfer cannot be made even comparatively permanent, unless an amount of care be taken in the making of it which is neither compatible nor consistent with the popular price and extensive output. How now stands the case with an argentic enlargement? Of course it may be said that there is scarcely time yet to make a fair comparison—that the argentic enlargements are still only on their trial.
I will give you my own experience. I mentioned at the outset that seven or eight years ago I had tried Kennet's pellicle and failed, but got one or two results which I retained as curiosities till only a month or two ago; but up to that time I cannot say they had faded in the least, and I have here a specimen made three years ago, which I have purposely subjected to very severe treatment. It has been exposed without any protection to the light and damp and all the other noxious influences of a Glasgow atmosphere, and although certainly tarnished, I think you will find that it has not faded; the whites are dirty, but the blacks have lost nothing of their original strength. I here show you the picture referred to, a 12 by 10 enlargement on artist's canvas, and may here state, in short, that my whole experience of argentic enlargements leads me to the conclusion that, setting aside every other quality, they are the most permanent pictures that have ever been produced. Chromotypes and other carbon pictures have been called permanent, but their permanence depends upon the nature of the pigment employed, and associated with the chromated gelatine in which they are produced, most of pigments used, and all of the prettiest ones, being unable to withstand the bleaching action of the light for more than a few weeks. Carbon pictures are therefore only permanent according to the degree in which the coloring matter employed is capable of resisting the decolorizing action of light. But there is no pigment in an argentic print, nothing but the silver reduced by the developer after the action of light; and that has been shown by, I think, Captain Abney, to be of a very stable and not easily decomposed nature; while if the pictures are passed through a solution of alum after washing and fixing, the gelatine also is so acted upon as to be rendered in a great degree impervious to the action of damp, and the pictures are then somewhat similar to carbon pictures without carbon.
I may now say a few words on the defects and failures sometimes met with in working this process; and first in regard to the yellowing of the whites. I hear frequent complaints of this want of purity in the whites, especially in vignetted enlargements, and I believe that this almost always arises from one or other of the two following causes:
First. An excess of the ferrous salt in the ferrous oxalate developer; and when this is the case, the yellow compound salt is more in suspension than solution, and in the course of development it is deposited upon, and at the same time formed in, the gelatinous film.
The proportions of saturated solution of oxalate to saturated solution of iron, to form the oxalate of iron developer, that has been recommended by the highest and almost only scientific authority on the subject—Dr. Eder—are from 4 to 6 parts of potassic oxalate to 1 part of ferrous sulphate.
Now while these proportions may be the best for the development of a negative, they are not, according to my experience, the best for gelatine bromide positive enlargements; I find, indeed, that potassic oxalate should not have more than one-eighth of the ferrous sulphate solution added to it, otherwise it will not hold in proper solution for any length of time the compound salt formed when the two are mixed.
The other cause is the fixing bath. This, for opals and vignetted enlargements especially, should always be fresh and pretty strong, so that the picture will clear rapidly before any deposit has time to take place, as it will be observed that very shortly after even one iron developed print has been fixed in it a deposit of some kind begins to take place, so that although it may be used a number of times for fixing prints that are meant to be colored afterward it is best to take a small quantity of fresh hypo for every enlargement meant to be finished in black and white. The proportions I use are 8 ounces to the pint of water. Almost the only other complaints I now hear are traceable to over-exposure or lack of intelligent cleanliness in the handling of the paper. The operator, after having been dabbling for some time in hypo, or pyro, or silver solution, gives his hands a wipe on the focusing cloth, and straightway sets about making an enlargement, ending up by blessing the manufacturer who sent him paper full of black stains and smears. Argentic paper is capable of yielding excellent enlargements, but it must be intelligently exposed, intelligently developed, and cleanly and carefully handled.
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THE MANUFACTURE AND CHARACTERISTICS OF PHOTOGRAPHIC LENSES.
At a recent meeting of the London and Provincial Photographic Association Mr. J. Traill Taylor, formerly of New York, commenced his lecture by referring to the functions of lenses, and by describing the method by which the necessary curves were computed in order to obtain a definite focal length. The varieties of optical glass were next discussed, and specimens (both in the rough and partly shaped state) were handed round for examination. The defects frequently met with in glass, such as striae and tears, were then treated upon; specimens of lenses defective from this cause were submitted to inspection, and the mode of searching for such flaws described. Tools for grinding and polishing lenses of various curvatures were exhibited, together with a collection of glass disks obtained from the factory of Messrs. Ross & Co., and in various stages of manufacture—from the first rough slab to the surface of highest polish. Details of polishing and edging were gone into, and a series of the various grades of emery used in the processes was shown. The lecturer then, by means of diagrams which he placed upon the blackboard, showed the forms of various makes of photographic lenses, and explained the influence of particular constructions in producing certain results; positive and negative spherical aberration, and the manner in which they are made to balance each other, was also described by the aid of diagrams, as was also chromatic aberration. He next spoke of the question of optical center of lenses, and said that that was not, as had been hitherto generally supposed, the true place from which to measure the focus of a lens or combination. This place was a point very near the optical center, and was known as the "Gauss" point, from the name of the eminent German mathematician who had investigated and made known its properties, the knowledge of which was of the greatest importance in the construction of lenses. A diagram was drawn to show the manner of ascertaining the two Gauss points of a bi-convex lens, and a sheet exhibited in which the various kinds of lenses with their optical centers and Gauss points were shown. For this drawing he (Mr. Taylor) said he was indebted to Dr. Hugo Schroeder, now with the firm of Ross & Co. The lecturer congratulated the newly-proposed member of the Society, Mr. John Stuart, for his enterprise in securing for this country a man of such profound acquirements. The subject of distortion was next treated of, and the manner in which the idea of a non distorting doublet could be evolved from a single bi-convex lens by division into two plano-convex lenses with a central diaphragm was shown. The influence of density of glass was illustrated by a description of the doublet of Steinheil, the parent of the large family of rapid doublets now known under various names. The effect of thickness of lenses was shown by a diagram of the ingenious method of Mr. F. Wenham, who had long ago by this means corrected spherical aberration in microscopic objective. The construction of portrait lenses was next gone into, the influence of the negative element of the back lens being especially noted. A method was then referred to of making a rapid portrait lens cover a very large angle by pivoting at its optical center and traversing the plate in the manner of the pantoscopic camera. The lecturer concluded by requesting a careful examination of the valuable exhibits upon the table, kindly lent for the occasion by Messrs. Ross & Co.
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IMPROVED DEVELOPERS FOR GELATINE PLATES.
By Dr. Eder.
We are indebted to Chas. Ehrmann, Esq., for the improved formulas given below as translated by him for the Photographic Times.
Dr. Eder has for a considerable time directed especial attention to the soda and potash developers, either of which seems to offer certain advantages over the ammoniacal pyrogallol. This advantage becomes particularly apparent with emulsions prepared with ammonia, which frequently show with ammoniacal developer green or red fog, or a fog of clayish color by reflected, and of pale purple by transmitted light. Ferrous oxalate works quite well with plates of that kind; so do soda and potassa developers.
For soda developers, Eder uses a solution of 10 parts of pure crystallized soda in 100 parts of water. For use, 100 c.c. of this solution are mixed with 6 c.c. of a pyrogallic solution of 1:10, without the addition of any bromide.
More pleasant to work with is Dr. Stolze's potassa developer. No. 1: Water, 200 c.c.; chem. pure potassium carbonate, 90 gr.; sodium sulphite, 25 gr. No. 2: Water 100 c.c.; citric, 11/2 gr.; sodium sulphite, 25 gr.; pyrogallol., 12 gr. Solution No. 2 is for its better keeping qualities preferable to Dr. Stolze's solution.[A] The solutions when in well stoppered bottles keep well for some time. To develop, mix 100 c.c. of water with 40 min. of No. 1 and 50 min. of No. 2. The picture appears quickly and more vigorously than with iron oxalate. If it is desirable to decrease the density of the negatives, double the quantity of water. The negatives have a greenish brown to olive-green tone. A very fine grayish-black can be obtained by using a strong alum bath between developing and fixing. The same bath after fixing does not act as effectual in producing the desired tone. A bath of equal volumes of saturated solutions of alum and ferrous sulphate gives the negative a deep olive-brown color and an extraordinary intensity, which excludes all possible necessities of an after intensification.
[Footnote A: 100 c.c. water; 10 c.c. alcohol; 10 gr. pyrogallol; 1 gr. salicylic acid.]
The sensitiveness with this developer is at least equal to that when iron developer is used, frequently even greater.
The addition of bromides is superfluous, sometimes injurious. Bromides in quantities, as added to ammoniacal pyro, would reduce the sensitiveness to 1/10 or 1/20; will even retard the developing power almost entirely.
Must a restrainer be resorted to, 1 to 3 min. of a 1:10 solution of potassium bromide is quite sufficient.
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THE PREPARATION OF LARD FOR USE IN PHARMACY.
[Footnote: Read at an evening meeting of the Pharmaceutical Society of Great Britain, November 7, 1883.]
By Professor REDWOOD.
I have read with much, interest the paper on "Ointment Bases," communicated by Mr. Willmott to the Pharmaceutical Conference at its recent meeting, but the part of the subject which has more particularly attracted my attention is that which relates to prepared lard. Reference is made by Mr. Willmott to lard prepared in different ways, and it appears from the results of his experiments that when made according to the process of the British Pharmacopoeia it does not keep free from rancidity for so long a time as some of the samples do which have been otherwise prepared. The general tendency of the discussion, as far as related to this part of the subject, seems to have been also in the same direction; but neither in the paper nor in the discussion was the question of the best mode of preparing lard for use in pharmacy so specially referred to or fully discussed as I think it deserves to be.
When, in 1860, Mr. Hills, at a meeting of the Pharmaceutical Society, suggested a process for the preparation of lard, which consisted in removing from the "flare" all matter soluble in water, by first thoroughly washing it in a stream of cold water after breaking up the tissues and afterward melting and straining the fat at a moderate heat, this method of operating seemed to be generally approved. It was adopted by men largely engaged in "rendering" fatty substances for use in pharmacy and for other purposes for which the fat was required to be as free as possible from flavor and not unduly subject to become rancid. It became the process of the British Pharmacopoeia in 1868. In 1869 it formed the basis of a process, which was patented in Paris and this country by Hippolite Mege, for the production of a fat free from taste and odor, and suitable for dietetic use as a substitute for butter. Mege's process consists in passing the fat between revolving rollers, together with a stream of water, and then melting at "animal heat." This process has been used abroad in the production of the fatty substance called oleomargarine.
But while there have been advocates for this process, of whom I have been one, opinions have been now and then expressed to the effect that the washing of the flare before melting the fat was rather hurtful than beneficial. I have reason to believe that this opinion has been gaining ground among those who have carefully inquired into the properties of the products obtained by the various methods which have been suggested for obtaining animal fat in its greatest state of purity.
I have had occasion during the last two or three years to make many experiments on the rendering and purification of animal fat, and at the same time have been brought into communication with manufacturers of oleomargarine on the large scale; the result of which experience has been that I have lost faith in the efficacy of the Pharmacopeia process. I have found that in the method now generally adopted by manufacturers of oleomargarine, which is produced in immense quantities, the use of water, for washing the fat before melting it, is not only omitted but specially avoided. The parts of the process to which most importance is attached are: First, the selection of fresh and perfectly sweet natural fat, which is hung up and freely exposed to air and light. It thus becomes dried and freed from an odor which is present in the freshly slaughtered carcass. It is then carefully examined, and adhering portions of flesh or membrane as far as possible removed; after which it is cut up and passed through a machine in which it is mashed so as to completely break up the membraneous vesicles in which the fat is inclosed. The magma thus produced is put into a deep jacketed pan heated by warm water, and the fat is melted at a temperature not exceeding 130 deg.F.
If the flare has been very effectually mashed, the fat may be easily melted away from the membraneous matter at 120 deg.F., or even below that, and no further continuance of the heat is required beyond what is necessary for effecting a separation of the melted fat from the membraneous or other suspended matter. Complete separation of all suspended matter is obviously important, and therefore nitration seems desirable, where practicable; which however is not on the large scale.
My experiments tend to indicate that the process just described is that best adapted for the preparation of lard for use in pharmacy. There is, however, a point connected with this or any other method of preparing lard which is deserving of more attention than it has, I believe, usually received, and that is, the source from which the flare has been derived. Everybody knows how greatly the quality of pork depends upon the manner in which the pig has been fed, and this applies to the fat as well as other parts of the animal. Some time ago I had some pork submitted to me for the expression of opinion upon it, which had a decided fishy flavor, both in taste and smell. This flavor was present in every part, fat and lean, and it is obvious that lard prepared from that fat would not be fit for use in pharmacy. The pig had been prescribed a fish diet. Barley meal would, no doubt, have produced a better variety of lard.
* * * * *
ANTI-CORROSION PAINT.
The Neueste Erfinderung describes an anti-corrosion paint for iron. It states that if 10 per cent. of burnt magnesia, or even baryta, or strontia, is mixed (cold) with ordinary linseed-oil paint, and then enough mineral oil to envelop the alkaline earth, the free acid of the paint will be neutralized, while the iron will be protected by the permanent alkaline action of the paint. Iron to be buried in damp earth may be painted with a mixture of 100 parts of resin (colophony), 25 parts of gutta-percha, and 50 parts of paraffin, to which 20 parts of magnesia and some mineral oil have been added.
* * * * *
CARBON IN STEEL.
At a recent meeting of the Chemical Society, London, a paper was read entitled "Notes on the Condition in which Carbon exists in Steel," by Sir F.A. Abel, C.B., and W.H. Deering.
Two series of experiments were made. In the first series disks of steel 2.5 inches in diameter and 0.01 inch thick were employed. They were all cut from the same strip of metal, but some were "cold-rolled," some "annealed," and some "hardened." The total carbon was found to be: "cold-rolled," 1.108 per cent.; hardened, 1.128 per cent.; and annealed, 0.924 and 0.860 per cent. Some of the disks were submitted to the action of an oxidizing solution consisting of a cold saturated solution of potassium bichromate with 5 per cent. by volume of pure concentrated sulphuric acid. In all cases a blackish magnetic residue was left undissolved. These residues, calculated upon 100 parts of the disks employed, had the following compositions: "Cold-rolled" carbon, 1.039 per cent.; iron, 5.871. Annealed, C, 0.83 per cent.; Fe, 4.74 per cent. Hardened, C, 0.178 per cent.; Fe, 0.70 per cent. So that by treatment with chromic acid in the cold nearly the whole of the carbon remains undissolved with the cold-rolled and annealed disks, but only about one-sixth of the total carbon is left undissolved in the case of the hardened disk. The authors then give a _resume_ of previous work on the subject. In the second part they have investigated the action of bichromate solutions of various strengths on thin sheet-steel, about 0.098 inch thick, which was cold-rolled and contained: Carbon, 1.144 per cent.; silica, 0.166 per cent.; manganese, 0.104 per cent. Four solutions were used. The first contained about 10 per cent. of bichromate and 9 per cent. of H_{2}SO_{4} by weight; the second was eight-tenths as strong, the third about half as strong, the fourth about one and a half times as strong. In all cases the amount of solution employed was considerably in excess of the amount required to dissolve the steel used. A residue was obtained as before. With solution 1, the residue contained, C, 1.021; sol. 2, C, 0.969; sol. 3, C 1.049 the atomic ratio of iron to carbon was Fe 2.694: C, 1; Fe, 2.65: C, 1; Fe), 2.867 C, 1): sol. 4. C, 0.266 per 100 of steel. The authors conclude that the carbon in cold rolled steel exists not simply diffused mechanically through the mass of steel but in the form of an iron carbide, Fe_{3}C, a definite product, capable of resisting the action of an oxidizing solution (if the latter is not too strong), which exerts a rapid solvent action upon the iron through which the carbide is distributed.
* * * * *
APPARATUS FOR EXTRACTING STARCH FROM POTATOES.
In the apparatus of Mr. Angele, of Berlin, shown in the annexed cuts (Figs. 1 and 2), the potatoes, after being cleaned in the washer, C, slide through the chute, v, into a rasp, D, which reduces them to a fine pulp under the action of a continuous current of water led in by the pipe, d. The liquid pulp flows into the iron reservoir, B, from whence a pump, P, forces it through the pipe, w, to a sieve, g, which is suspended by four bars and has a backward and forward motion. By means of a rose, c, water is sprinkled over the entire surface of the sieve and separates the fecula from the fibrous matter. The water, charged with fine particles of fecula, and forming a sort of milk, flows through the tube, z, into the lower part, N, of the washing apparatus, F, while the pulp runs over the sieve and falls into the grinding-mill, H. This latter divides all those cellular portions of the fecula that have not been opened by the rasp, and allows them to run, through the tube, h, into the washing apparatus, F, where the fecula is completely separated from woody fibers. The fluid pulp is carried by means of a helix, i, to a revolving perforated drum at e. From this, the milky starch flows into the jacket, N, while the pulp (ligneous fibers) makes its exit from the apparatus through the aperture, n, and falls into the reservoir, o.
The liquid from the jacket, N, passes to a refining sieve, K, which, like the one before mentioned, has a backward and forward motion, and which is covered with very fine silk gauze in order to separate the very finest impurities from the milky starch. The refined liquid then flows into the reservoir, m, and the impure mass of sediment runs into the pulp-reservoir, o. The pump, l, forces the milky liquid from the reservoir, m, to the settling back, while the pulp is forced by a pump, u, from the receptacle, o, into a large pulp-reservoir.
The water necessary for the manufacture is forced by the pump, a, into the reservoir, W, from whence it flows, through the pipes, r, into the different machines. All the apparatus are set in motion by two shaftings, q. The principal shaft makes two hundred revolutions per minute, but the velocity of that of the pumps is but fifty revolutions.—Polytech. Journ., and Bull. Musee de l'Indust.
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A SIMPLE APPARATUS FOR DESCRIBING ELLIPSES.
By Prof. E.J. HALLOCK.
A very simple apparatus for describing an oval or ellipse may be constructed by any apprentice or school boy as follows: Procure a straight piece of wood about 1/4 inch wide by 1/8 inch thick and 13 inches long. Beginning 1/2 inch from the end, bore a row of small holes only large enough for a darning needle to pass through and half an inch apart. Mark the first one (at A) 0, the third 1, the fifth 2, and so on to 12, so that the numbers represent the distance from O in inches. A small slit may be made in the end of the ruler or strip of wood near A, but a better plan is to attach a small clip on one side.
Next procure a strong piece of linen thread about four feet long; pass it through the eye of a coarse needle, wax and twist it until it forms a single cord. Pass the needle upward through the hole marked 0, and tie a knot in the end of the thread to prevent its slipping through. The apparatus is now ready for immediate use. It only remains to set it to the size of the oval desired.
Suppose it is required to describe an ellipse the longer diameter of which is 8 inches, and the distance between the foci 5 inches. Insert a pin or small tack loosely in the hole between 6 and 7, which is distant 6-1/2 inches from O. Pass the needle through hole 5, allowing the thread to pass around the tack or pin; draw it tightly and fasten it in the slit or clip at the end. Lay the apparatus on a smooth sheet of paper, place the point of a pencil at E, and keeping the string tight pass it around and describe the curve, just in the same manner as when the two ends of the string are fastened to the paper at the foci. The chief advantage claimed over the usual method is that it may be applied to metal and stone, where it is difficult to attach a string. On drawings it avoids the necessity of perforating the paper with pins.
As the pencil point is liable to slip out of the loop formed by the string, it should have a nick cut or filed in one side, like a crochet needle.
As the mechanic frequently wants to make an oval having a given width and length, but does not know what the distance between the foci must be to produce this effect, a few directions on this point may be useful:
It is a fact well known to mathematicians that if the distance between the foci and the shorter diameter of an ellipse be made the sides of a right angled triangle, its hypothenuse will equal the greater diameter. Hence in order to find the distance between the foci, when the length and width of the ellipse are known, these two are squared and the lesser square subtracted from the greater, when the square root of the difference will be the quantity sought. For example, if it be required to describe an ellipse that shall have a length of 5 inches and a width of 3 inches, the distance between the foci will be found as follows:
(5 x 5) - (3 x 3) = (4 x 4) or _ 25 - 9 = 16 and /16 = 4.
In the shop this distance may be found experimentally by laying a foot rule on a square so that one end of the former will touch the figure marking the lesser diameter on the latter, and then bringing the figure on the rule that represents the greater diameter to the edge of the square; the figure on the square at this point is the distance sought. Unfortunately they rarely represent whole numbers. We present herewith a table giving the width to the eighth of an inch for several different ovals when the length and distance between foci are given.
Length. Distance between foci. Width. Inches. Inches. Inches.
2 1 13/4 2 11/2 11/4
21/2 1 21/4 21/2 11/2 2 21/2 2 11/2
3 1 11/2 3 11/2 2-7/8 3 2 2-5/8 3 21/2 21/4
31/2 1 3-3/8 31/2 11/2 3-1/8 31/2 2 2-7/8 31/2 21/2 21/2 31/2 3 13/4
4 2 31/2 4 21/2 3-1/8 4 3 2-5/8 4 31/2 2
5 3 4 5 4 3
For larger ovals multiples of these numbers may be taken; thus for 7 and 4, take from the table twice the width corresponding to 31/2 and 2, which is twice 2-7/8, or 53/4. It will be noticed also that columns 2 and 3 are interchangeable.
To use the apparatus in connection with the table: Find the length of the desired oval in the first column of the table, and the width most nearly corresponding to that desired in the third column. The corresponding number in the middle column tells which hole the needle must be passed through. The tack D, around which the string must pass, is so placed that the total length of the string AD + DC, or its equal AE + EC, shall equal the greater diameter of the ellipse. In the figure it is placed 61/2 inches from A, and 11/2 inches from C, making the total length of string 8 inches. The oval described will then be 8 inches long and 61/4 inches wide.
The above table will be found equally useful in describing ovals by fastening the ends of the string to the drawing as is recommended in all the text books on the subject. On the other hand, the instrument may be set "by guess" when no particular accuracy is required.
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THE MANUFACTURE OF CHARCOAL IN KILNS.
The manufacture of charcoal in kilns was declared many years ago, after a series of experiments made in poorly constructed furnaces, to be unprofitable, and the subject is dismissed by most writers with the remark, that in order to use the method economically the products of distillation, both liquid and gaseous, must be collected. T. Egleston, Ph.D., of the School of Mines, New York, has read a paper on the subject before the American Institute of Mining Engineers, from which we extract as follows: As there are many SILVER DISTRICTS IN THE WEST where coke cannot be had at such a price as will allow of its being used, and where the ores are of such a nature that wood cannot be used in a reverberatory furnace, the most economical method of making charcoal is an important question.
Kilns for the manufacture of charcoal are made of almost any shape and size, determined in most cases by the fancy of the builder or by the necessities of the shape of the ground selected. They do not differ from each other in any principle of manufacture, nor does there seem to be any appreciable difference in the quality of the fuel they produce, when the process is conducted with equal care in the different varieties; but there is a considerable difference in the yield and in the cost of the process in favor of small over large kilns. The different varieties have come into and gone out of use mainly on account of the cost of construction and of repairs. The object of a kiln is to replace the cover of a meiler by a permanent structure. Intermediate between the meiler and the kiln is the Foucauld system, the object of which is to replace the cover by a structure more or less permanent, which has all the disadvantages of both systems, with no advantages peculiar to itself.
The kilns which are used may be divided into the rectangular, the round, and the conical, but the first two seem to be disappearing before the last, which is as readily built and much more easily managed.
ALL VARIETIES OF KILNS
Are usually built of red brick, or, rarely, of brick and stone together. Occasionally, refractory brick is used, but it is not necessary. The foundations are usually made of stone. There are several precautions necessary in constructing the walls. The brick should be sufficiently hard to resist the fire, and should therefore be tested before using. It is an unnecessary expense to use either second or third quality fire-brick. As the pyroligneous acid which results from the distillation of the wood attacks lime mortar, it is best to lay up the brick with fire-clay mortar, to which a little salt has been added; sometimes loam mixed with coal-tar, to which a little salt is also added, is used. As the principal office of this mortar is to fill the joints, special care must be taken in laying the bricks that every joint is broken, and frequent headers put in to tie the bricks together. It is especially necessary that all the joints should be carefully filled, as any small open spaces would admit air, and would materially decrease the yield of the kiln. The floor of the kiln was formerly made of two rows of brick set edgewise and carefully laid, but latterly it is found to be best made of clay. Any material, however, that will pack hard may be used. It must be well beaten down with paving mauls. The center must be about six inches higher than the sides, which are brought up to the bottom of the lower vents. Most kilns are carefully pointed, and are then painted on the outside with a wash of clay suspended in water, and covered with a coating of coal-tar, which makes them waterproof, and does not require to be renewed for several years.
The kilns were formerly roofed over with rough boards to protect the masonry from the weather, but as no special advantage was found to result from so doing, since of late years they have been made water-proof, the practice has been discontinued.
The wood used is cut about one and a fifth meters long. The diameter is not considered of much importance, except in so far as it is desirable to have it as nearly uniform as possible. When most of the wood is small, and only a small part of it is large, the large pieces are usually split, to make it pack well. It has been found most satisfactory to have three rows of vents around the kiln, which should be provided with a cast-iron frame reaching to the inside of the furnace. The vents near the ground are generally five inches high—the size of two bricks—and four inches wide—the width of one—and the holes are closed by inserting one or two bricks in them. They are usually the size of one brick, and larger on the outside than on the inside. These holes are usually from 0.45 m. to 0.60 m. apart vertically, and from 0.80 m. to 0.90 m. apart horizontally. The lower vents start on the second row of the brickwork above the foundation, and are placed on the level with the floor, so that the fire can draw to the bottom. There is sometimes an additional opening near the top to allow of the rapid escape of the smoke and gas at the time of firing, which is then closed, and kept closed until the kiln is discharged. This applies mostly to the best types of conical kilns. In the circular and conical ones the top charging door is sometimes used for this purpose. Hard and soft woods are burned indifferently in the kilns. Hard-wood coal weighs more than soft, and the hard variety of charcoal is usually preferred for blast furnaces, and for such purposes there is an advantage of fully 33-1/3 per cent. or even more in using hard woods. For the direct process in the bloomaries, soft-wood charcoal is preferred. It is found that it is not usually advantageous to build kilns of over 160 to 180 cubic meters in capacity. Larger furnaces have been used, and give as good a yield, but they are much more cumbersome to manage. The largest yield got from kilns is from 50 to 60 bushels for hard wood to 50 for soft wood. The average yield, however, is about 45 bushels. In meilers, two and a half to three cords of wood are required for 100 bushels, or 30 to 40 bushels to the cord. The kiln charcoal is very large, so that the loss in fine coal is very much diminished. The pieces usually come out the whole size, and sometimes the whole length of the wood.
The rectangular kilns were those which were formerly exclusively in use. They are generally built to contain from 30 to 90 cords of wood. The usual sizes are given in the table below:
1 2 3 4 Length 50 40 40 48 Width 12 15 14 17 Height 12 15 18 18 Capacity, in cords 55 70 75 90
1 and 2. Used in New England. 3. Type of those used in Mexico. 4. Kiln at Lauton, Mich.
The arch is usually an arc of a circle. A kiln of the size of No. 4, as constructed at the Michigan Central Iron Works, with a good burn, will yield 4,000 bushels of charcoal.
The vertical walls in the best constructions are 12 to 13 feet high, and 1-1/2 brick thick, containing from 20 to 52 bricks to the cubic foot of wall. To insure sufficient strength to resist the expansion and contraction due to the heating and cooling, they should be provided with buttresses which are 1 brick thick and 2 wide, as at Wassaic, New York; but many of them are built without them, as at Lauton, Michigan, as shown in the engraving. In both cases they are supported with strong braces, from 3 to 4 feet apart, made of round or hewn wood, or of cast iron, which are buried in the ground below, and are tied above and below with iron rods, as in the engraving, and the lower end passing beneath the floor of the kiln. When made of wood they are usually 8 inches square or round, or sometimes by 8 inches placed edgewise. They are sometimes tied at the top with wooden braces of the same size, which are securely fastened by iron rods running through the corners, as shown. When a number of kilns are built together, as at the Michigan Central Iron Works, at Lauton, Michigan, shown in the plan view, only the end kilns are braced in this way. The intermediate ones are supported below by wooden braces, securely fastened at the bottom. The roof is always arched, is one brick, or eight inches, thick, and is laid in headers, fourteen being used in each superficial foot. Many of the kilns have in the center a round hole, from sixteen to eighteen inches in diameter, which is closed by a cast iron plate. It requires from 35 M. to 40 M. brick for a kiln of 45 cords, and 60 M. to 65 M. for one of 90 cords.
* * * * *
The belief that population in the West Indies is stationary is so far from accurate that, as Sir Anthony Musgrave points out, it is increasing more rapidly than the population of the United Kingdom. The statistics of population show an increase of 16 per cent. on the last decennial period, while the increase in the United Kingdom in the ten years preceding the last census was under 11 per cent. This increase appears to be general, and is only slightly influenced by immigration. "The population of the West Indies," adds Sir A. Musgrave, "is now greater than that of any of the larger Australian colonies, and three times that of New Zealand."
* * * * *
HEAT DEVELOPED IN FORGING.
M. Tresca has lately presented to the Academy of Sciences some very interesting experiments on the development and distribution of heat produced by a blow of the steam hammer in the process of forging. The method used was as follows: The bar was carefully polished on both sides, and this polished part covered with a thin layer of wax. It was then placed on an anvil and struck by a monkey of known weight, P, falling from a height, H. The faces of the monkey and anvil were exactly alike, and care was taken that the whole work, T = PH, should be expended upon the bar. A single blow was enough to melt the wax over a certain zone; and this indicated clearly how much of the lateral faces had been raised by the shock to the temperature of melting wax. The form of this melted part could be made to differ considerably, but approximated to that of an equilateral hyperbola. Let A be the area of this zone, b the width of the bar, d the density, C the heat capacity, and t-t0 the excess of temperature of melting wax over the temperature of the air. Then, assuming that the area, A, is the base of a horizontal prism, which is everywhere heated to the temperature, t, the heating effect produced will be expressed by
Ab x d x C(t-t0)
Multiplying this by 425, or Joule's equivalent for the metrical system, the energy developed in heat is given by
T1 = 425 AbdC(t-t0).
Dividing T1 by T, we obtain the ratio which the energy developed in heat bears to the total energy of the blow.
With regard to the form of the zone of melting, it was found always to extend round the edges of the indent produced in the bar by the blow. We are speaking for the present of cases where the faces of the monkey and anvil were sharp. On the sides of the bar the zone took the form of a sort of cross with curved arms, the arms being thinner or thicker according to the greater or less energy of the shock. These forms are shown in Figs. 1 to 6. It will be seen that these zones correspond to the zones of greatest sliding in the deformation of a bar forged with a sharp edged hammer, showing in fact that it is the mechanical work done in this sliding which is afterward transformed into heat.
With regard to the ratio, above mentioned, between the heat developed and the energy of the blow, it is very much greater than had been expected when the other sources of loss were taken into consideration. In some cases it reached 80 per cent., and in a table given the limits vary for an iron bar between 68.4 per cent. with an energy of 40 kilogram-meters, and 83.6 per cent. with an energy of 90 kilogram-meters. With copper the energy is nearly constant at 70 per cent. It will be seen that the proportion is less when the energy is less, and it also diminishes with the section of the bar. This is no doubt due to the fact that the heat is then conducted away more rapidly. On the whole, the results are summed up by M. Tresca as follows:
(1) The development of heat depends on the form of the faces and the energy of the blow.
(2) In the case of faces with sharp edges, the process described allows this heat to be clearly indicated.
(3) The development of heat is greatest where the shearing of the material is strongest. This shearing is therefore the mechanical cause which produces the heating effect.
(4) With a blow of sufficient energy and a bar of sufficient size, about 80 per cent. of the energy reappears in the heat.
(5) The figures formed by the melted wax give a sort of diagram, showing the distribution of the heat and the character of the deformation in the bar.
(6) Where the energy is small the calculation of the percentage is not reliable.
So far we have spoken only of cases where the anvil and monkey have sharp faces. Where the faces are rounded the phenomena are somewhat different. Figs. 7 to 12 give the area of melted wax in the case of bars struck with blows gradually increasing in energy. It will be seen that, instead of commencing at the edges of the indent, the fusion begins near the middle, and appears in small triangular figures, which gradually increase in width and depth until at last they meet at the apex, as in Fig. 12. The explanation is that with the rounded edges the compression at first takes place only in the outer layers of the bar, the inner remaining comparatively unaffected. Hence the development of heat is concentrated on these outer layers, so long as the blows are moderate in intensity. The same thing had already been remarked in cases of holes punched with a rounded punch, where the burr, when examined, was found to have suffered the greatest compression just below the punch. With regard to the percentage of energy developed as heat, it was about the same as in the previous experiments, reaching in one case, with an iron bar and with an energy of 110 kilogram-meters, the exceedingly high figure of 91 per cent. With copper, the same figure varied between 50 and 60 per cent.—Iron.
* * * * *
A NOVEL PROPELLER ENGINE.
By Prof. C.W. MacCord.
The accompanying engravings illustrate the arrangement of a propeller engine of 20 inch bore and 22 inch stroke, whose cylinder and valve gear were recently designed by the writer, and are in process of construction by Messrs. Valk & Murdoch, of Charleston, S.C.
In the principal features of the engine, taken as a whole, as will be perceived, there is no new departure. The main slide valve, following nearly full stroke, is of the ordinary form, and reversed by a shifting link actuated by two eccentrics, in the usual manner; and the expansion valves are of the well known Meyer type, consisting of two plates on the back of the main valve, driven by a third eccentric, and connected by a right and left handed screw, the turning of which alters the distance between the plates and the point of cutting off.
The details of this mechanism, however, present several novel features, of which the following description will be understood by reference to the detached cuts, which are drawn upon a larger scale than the general plan shown in Figs. 1 and 2.
The first of these relates to the arrangement of the right and left handed screw, above mentioned, and of the device by which it is rotated.
Usually, the threads, both right handed and left handed, are cut upon the cut-off valve stem itself, which must be so connected with the eccentric rod as to admit of being turned; and in most cases the valve stem extends through both ends of the steam chest, so that it must both slide endwise and turn upon its axis in two stuffing boxes, necessarily of comparatively large size.
All this involves considerable friction, and in the engine under consideration an attempt has been made to reduce the amount of this friction, and to make the whole of this part of the gear neater and more compact, in the following manner:
Two small valve stems are used, which are connected at their lower ends by a crosstail actuated directly by the eccentric rod, and at their upper ends by a transverse yoke. This yoke, filling snugly between two collars formed upon a sleeve which it embraces, imparts a longitudinal motion to the latter, while at the same time leaving it free to rotate.
This sleeve has cut upon it the right and left handed screws for adjusting the cut-off valves; and it slides freely upon a central spindle which has no longitudinal motion, but, projecting through the upper end of the valve chest, can be turned at pleasure by means of a bevel wheel and pinion. The rotation of the spindle is communicated to the sleeve by means of two steel keys fixed in the body of the latter and projecting inwardly so as to slide in corresponding longitudinal grooves in the spindle.
Thus the point of cutting off is varied at will while the engine is running, by means of the hand wheel on the horizontal axis of the bevel pinion, and a small worm on the same axis turns the index, which points out upon the dial the distance followed. These details are shown in Figs. 3, 4, and 5; in further explanation of which it may be added that Fig. 3 is a front view of the valve chest and its contents, the cover, and also the balance plate for relieving the pressure on the back of the main valve (in the arrangement of which there is nothing new), being removed in order to show the valve stems, transverse yoke, sleeve, and spindle above described. Fig. 4 is a longitudinal section, and Fig. 5 is a transverse section, the right hand side showing the cylinder cut by a plane through the middle of the exhaust port, the left hand side being a section by a plane above, for the purpose of exhibiting more clearly the manner in which the steam is admitted to the valve chest; the latter having no pipes for this service, the steam enters below the valve, at each end of the chest, just as it escapes in the center.
The second noteworthy feature consists in this: that the cut-off eccentric is not keyed fast, as is customary when valve gear of this kind is employed, but is loose upon the shaft, the angular position in relation to the crank being changed when the engine is reversed; two strong lugs are bolted on the shaft, one driving the eccentric in one direction, the other in the opposite, by acting against the reverse faces of a projection from the side of The eccentric pulley.
The loose eccentric is of course a familiar arrangement in connection with poppet valves, as well as for the purpose of reversing an engine when driving a single slide valve. Its use in connection with the Meyer cut-off valves, however, is believed to be new; and the reason for its employment will be understood by the aid of Fig. 6.
For the purposes of this explanation we may neglect the angular vibrations of the connecting rod and eccentric rod, considering them both as of infinite length. Let O be the center of the shaft; let L O M represent the face of the main valve seat, in which is shown the port leading to the cylinder; and let A be the edge of the main valve, at the beginning of a stroke of the piston. It will then be apparent that the center of the eccentric must at that instant be at the point, C, if the engine turn to the left, as shown by the arrow, and at G, if the rotation be in the opposite direction; C and G then may be taken as the centers of the "go-ahead" and the "backing" eccentrics respectively, which operate the main valve through the intervention of the link.
Now, in each revolution of the engine, the cut-off eccentric in effect revolves in the same direction about the center of the main eccentric. Consequently, we may let R C S, parallel to L O M, represent the face of the cut-off valve seat, or, in other words, the back of the main valve, in which the port, C N, corresponds to one of those shown in Fig. 4; and the motion of the cut-off valve over this seat will be precisely, the same as though it were driven directly by an eccentric revolving around the center, C.
In determining the position of this eccentric, we proceed upon the assumption that the best results will be effected by such an arrangement that when cutting off at the earliest point required, the cut-off valve shall, at the instant of closing the port, be moving over it at its highest speed. And this requires that the center of the eccentric shall at the instant in question lie in the vertical line through C.
Next, the least distance to be followed being assigned, the angle through which the crank will turn while the piston is traveling that distance is readily found; then, drawing an indefinite line C T, making with the vertical line, G O, an angle, G C T. equal to the one thus determined, any point upon that line may be assumed as the position of the required center of the cut-off eccentric, at the beginning of the stroke.
But again, in order that the cut-off may operate in the same manner when backing as when going ahead, this eccentric must be symmetrically situated with respect to both C and G; and since L O M bisects and is perpendicular to G C, it follows that if the cut-off eccentric be fixed on the shaft, its center must be located at H, the intersection of C T with L M. This would require the edge of the cut-off valve at the given instant to be at Q, perpendicularly over H; and the travel over the main valve would be equal to twice C H, the virtual lever arm of the eccentric, the actual traverse in the valve chest being twice O H, the real eccentricity.
This being clearly excessive, let us next see what will occur if the lever arm, CH, be reduced as in the diagram to CK. The edge of the cut-off valve will then be at N; it instantly begins to close the port. CN, but not so rapidly as the main valve opens the port, AB.
The former motion increases in rapidity, while the latter decreases; therefore at some point they will become equal in velocity, and the openings of the two ports will be the same; and the question is, Will this maximum effective port area give a sufficient supply of steam?
This diagram is the same as the one actually used in the engine under consideration, in which it was required to follow a minimum distance of 5 inches in the stroke of 22. Under these conditions it is found that the actual port opening for that point of cutting off is three-fifths of that allowed when following full stroke, whereas the speed of the piston at the time when this maximum opening occurs is less than half its greatest speed.
This, it would seem, is ample; but we now find the eccentric, K, no longer in the right position for backing; when the engine is reversed it ought to be at, P, the angle, POL, being equal to the angle, KOL. By leaving it free, therefore, to move upon the shaft, by the means above described, through the angle, KOP, the desired object is accomplished. The real eccentricity is now reduced in the proportion of OK to OH, while the lengths of the cut-off valves, and what is equally important, their travel over the back of the main valve, are reduced in the proportion of CK to CH, in this instance nearly one-half; a gain quite sufficient to warrant the adoption of the expedient.
The third, and perhaps the most notable, peculiarity is the manner of suspending and operating the main link. As before stated, this link is used only for reversing, and is therefore always in "full gear" in one direction or the other; and the striking feature of the arrangement here used is that, whether going ahead or backing, there is no slipping of the link upon the link block.
The link itself is of the simplest form, being merely a curved flat bar, L, in which are two holes, A and B (Fig. 7), by which the link is hung upon the pins, which project from the sides of the eccentric rods at their upper ends.
This is most clearly shown in Fig. 8, which is a top view of the reversing gear. The link block is a socket, open on the side next to the eccentric rods, but closed on the side opposite, from which projects the journal, J, as shown in Fig. 9, which is a vertical section by the plane, XY. This journal turns freely in the outer end of a lever, M, which transmits the reciprocating motion to the valve, through the rock-shaft, O, and another lever, N. Connected with the lever, M, by the bridge-piece, K, and facing it, is a slotted arm, G, as shown in the end view, Fig. 10. The center line of this slot lies in the plane which contains the axes of the journal, J, and of the shaft, O.
A block, E, is fitted to slide in the slotted arm, G; and in this block is fixed a pin, P. A bridle-rod, R, connects P with the pin, A, of one of the eccentric-rods, prolonged for that purpose as shown in Fig. 8; and a suspension-rod, S, connects the same pin, P, with the upper end of the reversing lever, T, which is operated by the worm and sector. The distance, JO, in Fig. 10, or in other words the length of the lever, M, is precisely equal to the distance, AB, in Fig. 7, measured in a right line; and the rods, R and S, from center to center of the eyes, are also each of precisely this same length. Further, the axis about which the reversing lever, T, vibrates is so situated that when that lever, as in Fig 11, is thrown full to the left, the pin in its upper end is exactly in line with the rock-shaft, O.
When the parts are in this position, the suspension-rod, S, the arm, G, and the lever, M, will be as one piece, and their motions will be identical, consisting simply of vibration about the axis of the rock-shaft, O. The motion of the lever, M, is then due solely to the pin, B, which is in this case exactly in line with the journal, J, so that the result is the same as though this eccentric rod were connected directly to the lever; and the pin, P, being also in line with B and J, and kept so by the suspension-rod, S, it will be seen that the bridle-rod, R, will move with the link, L, as though the two were rigidly fastened together.
When the reversing lever, T, is thrown full to the right, as in Fig. 12, the pin, P, is drawn to the inner end of the slot in the arm, G, and is thus exactly in line with the rock-shaft, O. The suspension-rod, S, will, therefore, be at rest; but the pin, A, will have been drawn, by the bridle-rod, R, into line with the journal, J, and the bridle-rod itself will now vibrate with the lever, M, whose sole motion will be derived from the pin, A.
There is, then, no block slip whatever when the link thus suspended and operated is run in "full gear," either forward or backward.
If this arrangement be used in cases where the link is used as an expansion device, there will be, of course, some block slip while running in the intermediate gears. But even then, it is to be observed that the motion of the pin, A, relatively to the rocker arm is one of vibration about the moving center, J; and its motion relatively to the sliding block, E, is one of vibration about the center, P, whose motion relatively to E is a small amount of sliding in the direction of the slot, due to the fact that the rocker arm itself, which virtually carries the block, E, vibrates about O, while the suspension-rod, S, vibrates about another fixed center. It will thus be seen that, finally, the block slip will be determined by the difference in curvature of arcs which curve in the same direction, whether the engine be running forward or backward; whereas in the common modes of suspension the block slip in one direction is substantially the half sum of the curvatures of two arcs curving in opposite directions.
Consequently it would appear that the average action of the new arrangement would be at least equal to that of the old in respect to reducing the block slip when running in the intermediate gears, while in the full gears it entirely obviates that objectionable feature.
* * * * *
THE NEW RUSSIAN TORPEDO BOAT, THE POTI.
The Russian government has just had built at the shipyards of Mr. Normand, the celebrated Havre engineer, a torpedo boat called the Poti, which we herewith illustrate. This vessel perceptibly differs from all others of her class, at least as regards her model. Her extremities, which are strongly depressed in the upperworks, and the excessive inclination of her sides, give the boat as a whole a certain resemblance to the rams of our navy, such as the Taureau and Tigre.
A transverse section of the Poti approaches an ellipse in shape. Her water lines are exceedingly fine, and, in point of elegance, in no wise cede to those of the most renowned yachts. The vessel is entirely of steel, and her dimensions are as follows: Length, 28 meters; extreme breadth, 3.6 meters; depth, 2.5 meters; draught, 1.9 meters; displacement, 66 tons. The engine, which is a compound one, is of 600 H.P. The minimum speed required is 18 knots, or 33-34 meters, per hour, and it will probably reach 40 kilometers.
The vessel will be armed with 4 Whitehead torpedoes of 5.8 m., and 2 Hotchkiss guns of 40 cm. Her supply of coal will be sufficient for a voyage of 1000 nautical miles at a speed of 11 knots.—L'Illustration.
* * * * *
A NEW STEAMER PROPELLED BY HYDRAULIC REACTION.
The oar, the helix, and the paddle-wheel constitute at present the means of propulsion that are exclusively employed when one has recourse to a motive power for effecting the propulsion of a boat. The sail constitutes an entirely different mode, and should not figure in our enumeration, considering the essentially variable character of the force utilized.
In all these propellers, we have only an imitation, very often a rude one, of the processes which nature puts in play in fishes and mollusks, and the mode that we now wish to make known is without contradiction that which imitates these the best.
Hydraulic propulsion by reaction consists, in principle, in effecting a movement of boats, by sucking in water at the bow and forcing it out at the stern. This is a very old idea. Naturalists cite whole families of mollusks that move about in this way with great rapidity. It is probable that such was the origin of the first idea of this mode of operating. However this may be, as long ago as 1661 a patent was taken out in England, on this principle, by Toogood & Hayes. After this we find the patents of Allen (1729) and Rumsay (1788). In France, Daniel Bernouilli presented to the Academic des Sciences a similar project during the last century.
Mr. Seydell was the first to build a vessel on this principle. This ship, which was called the Enterprise, was of 100 tons burden, and was constructed at Edinburgh for marine fishery. The success of this was incomplete, but it was sufficient to show all the advantage that could be got from the idea. Another boat, the Albert, was built at Stettin, after the same type and at about the same epoch; and the question was considered of placing a reaction propeller upon the Great Eastern.
About 1860 the question was taken up again by the house of Cokerill de Seraing, which built the Seraing No. 2, that did service as an excursion boat between Liege and Seraing. The propeller of this consisted of a strong centrifugal pump, with vertical axis, actuated by a low pressure engine. This pump sucked water into a perforated channel at the bottom of the boat, and forced it through a spiral pipe to the propelling tubes. These latter consisted of two elbowed pipes issuing from the sides of the vessel and capable of pivoting in the exhaust ports in such a way as to each turn its mouth downward at will, backward or forward. The water expelled by the elbowed pipes reacted through pressure, as in the hydraulic tourniquet of cabinets of physics, and effected the propulsion of the vessel. Upon turning the two mouths of the propelling tubes backward, the boat was thrust forward, and, when they were turned toward the front, she was thrust backward. When one was turned toward the front and the other toward the stern, the boat swung around. Finally, when the two mouths were placed vertically the boat remained immovable. All the evolutions were easy, even without the help of the rudder, and the ways in which the propelling tubes could be placed were capable of being varied ad infinitum by a system of levers.
The Seraing No. 2 had an engine of a nominal power of 40 horses, and took on an average 30 minutes to make the trip, backward and forward, of 85 kilometers, with four stoppages.
The success obtained was perfect, and the running was most satisfactory. It was remarked, only, that from the standpoint of effective duty it would have been desirable to reduce the velocity of the water at its exit from the propellers.
Mr. Poillon attributes the small effective performance to the system employed for putting the water in motion. At time of Mr. Seraing's experiments, only centrifugal force pumps were known, and the theoretic effective duty of these, whatever be the peculiar system of construction, cannot exceed 66 per cent., and, in practice, falls to 40 or 50 per cent. in the majority of cases.
It is probable, then, that in making use of those new rotary pumps where effective duty reaches and often exceeds 80 per cent., we might obtain much better results, and it is this that justifies the new researches that have been undertaken by Messrs. Maginot & Pinette, whose first experiments we are about to make known.
In order to have it understood what interest attaches to these researches, let us state the principal advantages that this mode of propulsion will have over the helix and paddle wheel: The width of side-wheel boats will be reduced by from 20 to 30 per cent., and the draught of water will be diminished in screw steamers to that of the hull itself; the maneuver in which the power of the engine might be directly employed will be simplified; a machine will be had of a sensibly constant speed, and without change in its running; the production of waves capable of injuring the banks of canals will be avoided; the propeller will be capable of being utilized as a bilge pump; all vibration will be suppressed; the boat will be able to run at any speed under good conditions, while the helix works well only when the speed of the vessel corresponds to its pitch; it will be possible to put the propelling apparatus under water; and, finally, it will be possible to run the pump directly by the shaft of the high speed engine, without intermediate gearing, which is something that would prove a very great advantage in the case of electric pleasure boats actuated by piles and accumulators and dynamo-electric machines.
We now arrive at Messrs. Maginot & Pinette's system, the description of which will be greatly facilitated by the diagram that accompanies this article. The inventors have employed a boat 14 meters in length by 1.8 m. in width, and 65 centimeters draught behind and 32 in front. The section of the midship beam is 70 square decimeters, and that of the exhaust port is 4. At a speed of 2.2 meters per second the tractive stress, K, is from 10 to 11 kilogrammes. At a speed of 13.5 kilometers per hour, or 3.75 meters per second, the engine develops a power of 12 horses. The piston is 19 centimeters in diameter, and has a stroke of 15 centimeters. The shaft, in common, of the pump and engine makes 410 revolutions per minute. It will be seen from the figure that suction occurs at the lower part of the hull, at A, and that the water is forced out at B, to impel the vessel forward. C and C' are the tubes for putting the vessel about, and DD' the tubes for causing her to run backward. Owing to the tubes, C, C', the rudder has but small dimensions and is only used for directing the boat. The vessel may be turned about in situ by opening one of the receiving tubes, according to the side toward which it is desired to turn.
This boat is as yet only in an experimental state, and the first trials of her that have recently been made upon the Saone have shown the necessity of certain modifications that the inventors are now at work upon.—La Nature.
* * * * *
A NEW FORM OF FLEXIBLE BAND DYNAMOMETER.
[Footnote: Read before Section G of British Association.]
By Professor W.C. UNWIN.
In the ordinary strap dynamometer a flexible band, sometimes carrying segments of wood blocks, is hung over a pulley rotated by the motor, the power of which is to be measured. If the pulley turns with left-handed rotation, the friction would carry the strap toward the left, unless the weight, Q, were greater than P. If the belt does not slip in either direction when the pulley rotates under it, then Q-P exactly measures the friction on the surface of the pulley; and V being the surface velocity of the pulley (Q-P)V, is exactly the work consumed by the dynamometer. But the work consumed in friction can be expressed in another way. Putting [theta] for the arc embraced by the belt, and [mu] for the coefficient of friction,
Q/P = [epsilon]^{[mu]^{[theta]}},
or for a given arc of contact Q = [kappa]P, where [kappa] depends only on the coefficient of friction, increasing as [mu] increases, and vice versa. Hence, for the belt to remain at rest with two fixed weights, Q and P, it is necessary that the coefficient of friction should be exactly constant. But this constancy cannot be obtained. The coefficient of friction varies with the condition of lubrication of the surface of the pulley, which alters during the running and with every change in the velocity and temperature of the rubbing surfaces. Consequently, in a dynamometer in this simple form more or less violent oscillations of the weights are set up, which cannot be directly controlled without impairing the accuracy of the dynamometer. Professors Ayrton and Perry have recently used a modification of this dynamometer, in which the part of the cord nearest to P is larger and rougher than the part nearest to Q. The effect of this is that when the coefficients of friction increase, Q rises a little, and diminishes the amount of the rougher cord in contact, and vice versa. Thus reducing the friction, notwithstanding the increase of the coefficient. This is very ingenious, and the only objection to it, if it is an objection, is that only a purely empirical adjustment of the friction can be obtained, and that the range of the adjustment cannot be very great. If in place of one of the weights we use a spring balance, as in Figs. 2 and 3, we get a dynamometer which automatically adjusts itself to changes in the coefficient of friction.
For any increase in the coefficient, the spring in Fig. 2 lengthens, Q increases, and the frictional resistance on the surface of the pulley increases, both in consequence of the increase of Q, which increases the pressure on the pulley, and of the increase of the coefficient of friction. Similarly for any increase of the coefficient of friction, the spring in Fig. 3 shortens, P diminishes, and the friction on the surface of the pulley diminishes so far as the diminution of P diminishes the normal pressure, but on the whole increases in consequence of the increase of the coefficient of friction. The value of the friction on the surface of the pulley, however, is more constant for a given variation of the frictional coefficient in Fig. 3 than in Fig. 2, and the variation of the difference of tensions to be measured is less. Fig. 3, therefore, is the better form.
A numerical calculation here may be useful. Supposing the break set to a given difference of tension, Q-P, and that in consequence of any cause the coefficient of friction increases 20 per cent., the difference of tensions for an ordinary value of the coefficient of friction would increase from 1.5 P to 2 P in Fig. 2, and from 1.5 P to 1.67 P in Fig. 3. That is, the vibration of the spring, and the possible error of measurement of the difference of tension would be much greater in Fig. 2 than in Fig. 3. It has recently occurred to the author that a further change in the dynamometer would make the friction on the pulley still more independent of changes in the coefficient of friction, and consequently the measurement of the work absorbed still more accurate. Suppose the cord taken twice over a pulley fixed on the shaft driven by the motor and round a fixed pulley, C.
For clearness, the pulleys, A B, are shown of different sizes, but they are more conveniently of the same size. Further, let the spring balance be at the free end of the cord toward which the pulley runs. Then it will be found that a variation of 20 per cent. in the friction produces a somewhat greater variation of P than in Fig. 3. But P is now so much smaller than before that Q-P is much less affected by any error in the estimate of P. An alteration of 20 per cent. in the friction will only alter the quantity Q-P from 5.25 P to 5.55 P, or an alteration of less than 6 per cent.
To put it in another way, the errors in the use of dynamometer are due to the vibration of the spring which measures P, and are caused by variations of the coefficient of friction of the dynamometer. By making P very much smaller than in the usual form of the dynamometer, any errors in determining it have much less influence on the measurement of the work absorbed. We may go further. The cord may be taken over four pulleys; in that case a variation of 20 per cent. in the frictional coefficient only alters the total friction on the pulleys 11/4 percent. P is now so insignificant compared with Q that an error in determining it is of comparatively little consequence.
The dynamometer is now more powerful in absorbing work than in the form Fig. 3. As to the practical construction of the brake, the author thinks that simple wires for the flexible bands, lying in V grooves in the pulleys, of no great acuteness, would give the greatest resistance with the least variation of the coefficient of friction; the heat developed being in that case neutralized by a jet of water on the pulley. It would be quite possible with a pulley of say 3 feet diameter, and running at 50 feet of surface velocity per second, to have a sufficiently flexible wire, capable of carrying 100 lb. as the greater load, Q. Now with these proportions a brake of the form in Fig. 3 would, with a probable value of the coefficient of friction, absorb 6 horse power. With a brake in the form Fig. 4, 8.2 horse power would be absorbed; and with a brake in the form Fig. 5, 8.8 horse power would be absorbed. But since it would be easy to have two, three, or more wires side by side, each carrying its load of 100 lb., large amounts of horsepower could be conveniently absorbed and measured.
* * * * *
SEE'S GAS STOVE.
This stove consists of two or more superposed pipes provided with radiators. A gas burner is placed at the entrance of either the upper or lower pipe, according to circumstances. The products of combustion are discharged through a pipe of small diameter, which may be readily inserted into an already existing chimney or be hidden behind the wainscoting. The heat furnished by the gas flame is so well absorbed by radiation from the radiator rings that the gases, on making their exit, have no longer a temperature of more than from 35 to 40 degrees.
The apparatus, which is simple, compact, and cheap, is surrounded on all sides with an ornamented sheet iron casing. Being entirely of cast iron, it will last for a long time. The joints, being of asbestos, are absolutely tight, so as to prevent the escape of bad odors. The water due to the condensation of the gases is led through a small pipe out of doors or into a vessel from whence it may evaporate anew, so as not to change the hygrometric state of the air. The consumption of gas is very small, it taking but 250 liters per hour to heat a room of 80 cubic meters to a temperature of 18 deg. C.—Revue Industrielle.
* * * * *
The number of persons killed by wild animals and snakes in India last year was 22,125, against 21,427 in the previous year, and of cattle, 46,707, against 44,669. Of the human beings destroyed, 2,606 were killed by wild animals, and 19,519 by snakes. Of the deaths occasioned by the attacks of wild animals, 895 were caused by tigers, 278 by wolves, 207 by leopards, 356 by jackals, and 202 by alligators; 18,591 wild animals and 322,421 snakes were destroyed, for which the Government paid rewards amounting to 141,653 rupees.
* * * * *
RECTIFICATION OF ALCOHOL BY ELECTRICITY.
Some time ago, Mr. Laurent Naudin, it will be remembered,[1] devised a method of converting the aldehydes that give a bad taste and odor to impure spirits, into alcohol, through electrolytic hydrogen, the apparatus first employed being a zinc-copper couple, and afterward electrolyzers with platinum plates.
[Footnote 1: See SCIENTIFIC AMERICAN SUPPLEMENT of July 29, 1882, p. 5472.]
His apparatus had been in operation for several months, in the distillery of Mr. Boulet, at Bapeaume-les-Rouen, when a fire in December, 1881, completely destroyed that establishment. In reconstructing his apparatus, Mr. Naudin has availed himself of the experience already acquired, and has necessarily had to introduce important modifications and simplifications into the process. In the zinc-copper couple, he had in the very first place proposed to employ zinc in the form of clippings; but the metal in this state presents grave inconveniences, since the subsidence of the lower part, under the influence of the zinc's weight, soon proves an obstacle to the free circulation of the liquids, and, besides this, the cleaning presents insurmountable difficulties. This is why he substituted for the clippings zinc in straight and corrugated plates such as may be easily found in commerce. The management and cleaning of the pile thus became very simple.
The apparatus that contains the zinc-copper couple now has the form shown in Fig. 1. It may be cylindrical, as here represented, or, what is better, rectangular, because of the square form under which the sheets of zinc are found in commerce.
In this vessel of wood or iron plate, P, the corrugated zinc plates, b, b', b", are placed one above the other, each alternating with a flat one, a, a', a". These plates have previously been scoured, first with a weak solution of caustic soda in order to remove every trace of fatty matter derived from rolling, and then with very dilute hydrochloric acid, and finally are washed with common water. In order to facilitate the disengagement of hydrogen during the reaction, care must be taken to form apertures in the zinc plates, and to incline the first lower row with respect to the bottom of the vessel. A cubical pile of 150 hectoliters contains 105 rows of No. 16 flat and corrugated zinc plates, whose total weight is 6,200 kilogrammes. We obtain thus a hydrogenizing surface of 1,800 square meters, or 12 square meters per hectoliter of impure spirits of 50 deg. to 60 deg. Gay-Lussac. The raw impure spirits enter the apparatus through the upper pipe, E, and, after a sufficient stay therein, are drawn off through the lower pipe, H, into a reservoir, R, from whence, by means of a pump, they are forced to the rectifier.
The hydrogen engendered during the electrolysis is disengaged through an aperture in the cover of the pile. |
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