For studying the action of fluorine on gases, a special piece of apparatus, shown in Fig. 3, has been constructed. It is composed of a tube of platinum, fifteen centimeters long, closed by two plates of clear, transparent, and colorless fluorspar, and carrying three lateral narrower tubes also of platinum. Two of these tubes face each other in the center of the apparatus, and serve one for the conveyance of the fluorine and the other of the gas to be experimented upon. The third, which is of somewhat greater diameter than the other two, serves as exit tube for the product or products of the reaction, and may be placed in connection with a trough containing either water or mercury.

The apparatus is first filled with the gas to be experimented upon, then the fluorine is allowed to enter, and an observation of what occurs may be made through the fluorspar windows. One most important precaution to take in collecting the gaseous products over mercury is not to permit the platinum delivery tube to dip more than two or at most three millimeters under the mercury, as otherwise the levels of the liquid in the two limbs of the electrolysis U-tube become so different, owing to the pressure, that the fluorine from one side mixes with the hydrogen evolved upon the other, and there is a violent explosion.



ACTION OF FLUORINE UPON THE NON-METALLIC ELEMENTS.

Hydrogen.—As just described, hydrogen combines with fluorine, even at -23 deg. and in the dark, with explosive force. This is the only case in which two elementary gases unite directly without the intervention of extraneous energy. If the end of the tube delivering fluorine is placed in an atmosphere of hydrogen, a very hot blue flame, bordered with red, at once appears at the mouth of the tube, and vapor of hydrofluoric acid is produced.

Oxygen.—Fluorine has not been found capable of uniting with oxygen up to a temperature of 500 deg.. On ozone, however, it appears to exert some action, as will be evident from the following experiment. It was shown in 1887 that fluorine decomposes water, forming hydrofluoric acid, and liberating oxygen in the form of ozone. When a few drops of water are placed in the apparatus shown in Fig. 3, and fluorine allowed to enter, the water is instantly decomposed, and on looking through the fluorspar ends a thick dark cloud is seen over the spot where each drop of water had previously been. This cloud soon diminishes in intensity, and is eventually replaced by a beautiful blue gas—ozone in a state of considerable density. If the product is chased out by a stream of nitrogen as soon as the dense cloud is formed, a very strong odor is perceived, different from that of either fluorine or ozone, but which soon gives place to the unmistakable odor of ozone. It appears as if there is at first produced an unstable oxide of fluorine, which rapidly decomposes into fluorine and ozone.

Nitrogen and chlorine appear not to react with fluorine.

_Sulphur._—In contact with fluorine gas, sulphur rapidly melts and inflames. A gaseous fluoride of sulphur is formed, which possesses a most penetrating odor, somewhat resembling that of chloride of sulphur. The gas is incombustible, even in oxygen. When warmed in a glass vessel, the latter becomes etched, owing to the formation of silicon tetrafluoride, SiF_{4}. Selenium and tellurium behave similarly, but form crystalline solid fluorides.

Bromine vapor combines with fluorine in the cold with production of a very bright but low temperature dame. If the fluorine is evolved in the midst of pure dry liquid bromine, the combination is immediate, and occurs without flame.

Iodine.—When fluorine is passed over a fragment of iodine contained in the horizontal tube, combination occurs, with production of a pale flame. A very heavy liquid, colorless when free from dissolved iodine, and fuming strongly in the air, condenses in the cooled receiver. This liquid fluoride of iodine attacks glass with great energy and decomposes water when dropped into that liquid with a noise like that produced by red-hot iron. Its properties agree with those of the fluoride of iodine prepared by Gore by the action of iodine on silver fluoride.

Phosphorus.—Immediately phosphorus, either the ordinary yellow variety or red phosphorus, comes in contact with fluorine, a most lively action occurs, accompanied by vivid incandescence. If the fluorine is in excess, a fuming gas is evolved, which gives up its excess of fluorine on collecting over mercury, and is soluble in water. This gas is phosphorus pentafluoride, PF{5}, prepared some years ago by Prof. Thorpe. If, on the contrary, the phosphorus is in excess, a gaseous mixture of this pentafluoride with a new fluoride, the trifluoride, PF{3}, a gas insoluble in water, but which may be absorbed by caustic potash, is obtained. The trifluoride, in turn, combines with more fluorine to form the pentafluoride, the reaction being accompanied by the appearance of a flame of comparatively low temperature.

Arsenic combines with fluorine at the ordinary temperature with incandescence. If the current of fluorine is fairly rapid, a colorless fuming liquid condenses in the receiver, which is mainly arsenic trifluoride, AsF{3}, but which appears also to contain a new fluoride, the pentafluoride, AsF{5}, inasmuch as the solution in water yields the reactions of both arsenious and arsenic acids.

_Carbon._—Chlorine does not unite with carbon even at the high temperature of the electric arc, but fluorine reacts even at the ordinary temperature with finely divided carbon. Purified lampblack inflames instantly with great brilliancy, as do also the lighter varieties of wood charcoal. A curious phenomenon is noticed with wood charcoal; it appears at first to absorb and condense the fluorine, then quite suddenly it bursts into flame with bright scintillations. The denser varieties of charcoal require warming to 50 deg. or 60 deg. before they inflame, but it once the combustion is started at any point it rapidly propagates itself throughout the entire piece. Graphite must be heated to just below dull redness in order to effect combination; while the diamond has not yet been attacked by fluorine, even at the temperature of the Bunsen flame. A mixture of gaseous fluorides of carbon are produced whenever carbon of any variety is acted upon by fluorine, the predominating constituent being the tetrafluoride, CF_{4}.

_Boron._—The amorphous variety of boron inflames instantly in fluorine, with projection of brilliant sparks and liberation of dense fumes of boron trifluoride, BF_{3}. The adamantine modification behaves similarly if powdered. When the experiment is performed in the fluorspar tube, the gaseous fluoride may be collected over mercury. The gas fumes strongly in the air, and is instantly decomposed by water.

_Silicon._—The reaction between fluorine and silicon is one of the most beautiful of all these extraordinary manifestations of chemical activity. The cold crystals become immediately white-hot, and the silicon burns with a very hot flame, scattering showers of star-like, white-hot particles in all directions. If the action is stopped before all the silicon is consumed, the residue is found to be fused. As crystalline silicon only melts at a temperature superior to 1,200 deg., the heat evolved must be very great. If the reaction is performed in the fluorspar tube, the resulting gaseous silicon tetrafluoride, SiF_{4}, may be collected over mercury.

Amorphous silicon likewise burns with great energy in fluorine.

ACTION OF FLUORINE UPON METALS.

Sodium and potassium combine with fluorine with great vigor at ordinary temperatures, becoming incandescent, and forming their respective fluorides, which may be obtained crystallized from water in cubes. Metallic calcium also burns in fluorine gas, forming the fused fluoride, and occasionally minute crystals of fluorspar. Thallium is rapidly converted to fluoride at ordinary temperatures, the temperature rising until the metal melts and finally becomes red hot. Powdered magnesium burns with great brilliancy. Iron, reduced by hydrogen, combines in the cold with immediate incandescence, and formation of an anhydrous, readily soluble, white fluoride. Aluminum, on heating to low redness, gives a very beautiful luminosity, as do also chromium and manganese. The combustion of slightly warmed zinc in fluorine is particularly pretty as an experiment, the flame being of a most dazzling whiteness. Antimony takes fire at the ordinary temperature, and forms a solid white fluoride. Lead and mercury are attacked in the cold, as previously described, the latter with great rapidity. Copper reacts at low redness, but in a strangely feeble manner, and the white fumes formed appear to combine with a further quantity of fluorine to form a perfluoride. The main product is a volatile white fluoride. Silver is only slowly attacked in the cold. When heated, however, to 100 deg., the metal commences to be covered with a yellow coat of anhydrous fluoride, and on heating to low redness combination occurs, with incandescence, and the resulting fluoride becomes fused, and afterward presents a satin-like aspect. Gold becomes converted into a yellow deliquescent volatile fluoride when heated to low redness, and at a slightly higher temperature the fluoride is dissociated into metallic gold and fluorine gas.

The action of fluorine on _platinum_ has been studied with special care. It is evident, in view of the corrosion of the positive platinum terminal of the electrolysis apparatus, that nascent fluorine rapidly attacks platinum at a temperature of -23 deg.. At 100 deg., however, fluorine gas appears to be without action on platinum. At 500 deg.-600 deg. it is attacked strongly, with formation of the tetrafluoride. PtF_{4}, and a small quantity of the protofluoride, PtF_{2}. If the fluorine is admixed with vapor of hydrofluoric acid, the reaction is much more vigorous, as if a fluorhydrate of the tetrafluoride, perhaps 2HF.PtF_{4}, were formed. The tetrafluoride is generally found in the form of deep-red fused masses, or small yellow crystals resembling those of anhydrous platinum chloride. The salt is volatile and very hygroscopic. Its behavior with water is peculiar. With a small quantity of water a brownish yellow solution is formed, which, however, in a very short time becomes warm and the fluoride decomposes; platinic hydrate is precipitated, and free hydrofluoric acid remains in solution. If the quantity of water is greater, the solution may be preserved for some minutes without decomposition. If the liquid is boiled, it decomposes instantly. At a red heat platinic fluoride decomposes into metallic platinum and fluorine, which is evolved in the free state. This reaction can therefore be employed as a ready means of preparing fluorine, the fluoride only requiring to be heated rapidly to redness in a platinum tube closed at one end, when crystallized silicon held at the open end will be found to immediately take fire in the escaping fluorine. The best mode of obtaining the fluoride of platinum for this purpose is to heat a bundle of platinum wires to low redness in the fluorspar reaction tube in a rapid stream of fluorine. As soon as sufficient fluoride is formed on the wires, they are transferred to a well stoppered dry glass tube, until required for the preparation of fluorine.

ACTION OF FLUORINE UPON NON-METALLIC COMPOUNDS.

Sulphureted Hydrogen.—When the horizontal tube shown in Fig. 3 is filled with sulphureted hydrogen gas and fluorine is allowed to enter, a blue flame is observed on looking through the fluorspar windows playing around the spot where the fluorine is being admitted. The decomposition continues until the whole of the hydrogen sulphide is converted into gaseous fluorides of hydrogen and sulphur.

Sulphur dioxide is likewise decomposed in the cold, with production of a yellow flame and formation of fluoride of sulphur.

Hydrochloric acid gas is also decomposed at ordinary temperatures with flame, and, if there is not a large excess of hydrochloric acid present, with detonation. Hydrofluoric acid and free chlorine are the products.

Gaseous hydrobromic and hydriodic acids react with fluorine in a similar manner, with production of flame and formation of hydrofluoric acid. Inasmuch, however, as bromine and iodine combine with fluorine, as previously described, these halogens do not escape, but burn up to their respective fluorides. When fluorine is delivered into an aqueous solution of hydriodic acid, each bubble as it enters produces a flash of flame, and if the fluorine is being evolved fairly rapidly there is a series of very violent detonations. A curious reaction also occurs when fluorine is similarly passed into a 50 per cent. aqueous solution of hydrofluoric acid itself, a flame being produced in the middle of the liquid, accompanied by a series of detonations.

Nitric acid vapor reacts with great violence with fluorine, a loud explosion resulting. If fluorine is passed into the ordinary liquid acid, each bubble as it enters produces a flame in the liquid.

Ammonia gas is decomposed by fluorine with formation of a yellow flame, forming hydrofluoric acid and liberating nitrogen. With a solution of the gas in water, each bubble of fluorine produces an explosion and flame, as in case of hydriodic acid.

Phosphoric anhydride, when heated to low redness, burns with a pale flame in fluorine, forming a gaseous mixture of fluorides and oxyfluoride of phosphorus. Pentachloride and trichloride of phosphorus both react most energetically with fluorine, instantly producing a brilliant flame, and evolving a mixture of phosphorus pentafluoride and free chlorine.

_Arsenious anhydride_ also affords a brilliant combustion, forming the liquid trifluoride of arsenic, AsF_{3}. This liquid in turn appears to react with more fluorine with considerable evolution of heat, probably forming the pentafluoride, AsF_{5}. _Chloride of arsenic_, AsCl_{3}, is converted with considerable energy to the trifluoride, free chlorine being liberated.

Carbon bisulphide inflames in the cold in contact with fluorine, and if the fluorine is led into the midst of the liquid a similar production of flame occurs under the surface of the liquid, as in case of nitric acid. No carbon is deposited, both the carbon and sulphur being entirely converted into gaseous fluorides.

_Carbon tetrachloride_, as previously mentioned, reacts only very slowly with fluorine. The liquid may be saturated with gaseous fluorine at 15 deg., but on boiling this liquid a gaseous mixture is evolved, one constituent of which is carbon tetrafluoride, CF_{4}, a gas readily capable of absorption by alcoholic potash. The remainder consists of another fluoride of carbon, incapable of absorption by potash and chlorine. A mixture of the vapors of carbon tetrachloride and fluorine inflames spontaneously with detonation, and chlorine is liberated without deposition of carbon.

Boric anhydride is raised to a most vivid incandescence by fluorine, the experiment being rendered very beautiful by the abundant white fumes of the trifluoride which are liberated.

Silicon dioxide, one of the most inert of substances at the ordinary temperature, takes fire in the cold in contact with fluorine, becoming instantly white-hot, and rapidly disappearing in the form of silicon tetrafluoride. The chlorides of both boron and silicon are decomposed by fluorine, with formation of fluorides and liberation of chlorine, the reaction being accompanied by the production of flame.

ACTION OF FLUORINE UPON METALLIC COMPOUNDS.

Chlorides of the metals are instantly decomposed by fluorine, generally at the ordinary temperature, and in certain cases, antimony trichloride for instance, with the appearance of flame. Chlorine is in each case liberated, and a fluoride of the metal formed. A few require heating, when a similar decomposition occurs, often accompanied by incandescence, as in case of chromium sesquichloride.

Bromides and iodides are decomposed with even greater energy, and the liberated bromine and iodine burn in the fluorine with formation of their respective fluorides.

Cyanides react in a most beautiful manner with fluorine, the displaced cyanogen burning with a purple flame. Potassium ferrocyanide in particular affords a very pretty experiment, and reacts in the cold. Ordinary potassium cyanide requires slightly warming in order to start the combustion.

Fused potash yields potassium fluoride and ozone. Aqueous potash does not form potassium hypofluorite when fluorine is bubbled into it, but only potassium fluoride. Lime becomes most brilliantly incandescent, owing partly to the excess being raised to a very high temperature by the heat developed during the decomposition, and partly to the phosphorescence of the calcium fluoride formed.

Sulphides of the alkalies and alkaline earths are also immediately rendered incandescent, fluorides of the metal and sulphur being respectively formed.

Boron nitride behaves in an exceedingly beautiful manner, being attacked in the cold, and emitting a brilliant blue light which is surrounded by a halo of the fumes of boron fluoride.

_Sulphates_, _nitrates_ and _phosphates_ generally require the application of more or less heat, when they too are rapidly and energetically decomposed. Calcium phosphate is attacked in the cold like lime, giving out a brilliant white light, and producing calcium fluoride and gaseous oxyfluoride of phosphorus, POF_{3}. _Calcium carbonate_ also becomes raised to brilliant incandescence when exposed to fluorine gas, as does also normal _sodium carbonate_; but curiously enough the bicarbonates of the alkalies do not react with fluorine even at red heat. Perhaps this may be explained by the fact that fluorine has no action at available temperatures upon carbon dioxide.

ACTION OF FLUORINE UPON A FEW ORGANIC COMPOUNDS.

Chloroform.—When chloroform is saturated with fluorine, and subsequently boiled, carbon tetrafluoride, hydrofluoric acid and chlorine are evolved. If a drop of chloroform is agitated in a glass tube with excess of fluorine, a violent explosion suddenly occurs, accompanied by a flash of flame, and the tube is shattered to pieces. The reaction is very lively when fluorine is evolved in the midst of a quantity of chloroform, a persistent flame burns beneath the surface of the liquid, carbon is deposited, and fluorides of hydrogen and carbon are evolved together with chlorine.

Methyl chloride is decomposed by fluorine, even at -23 deg., with production of a yellow flame, deposition of carbon, and liberation of fluorides of hydrogen and carbon and free chlorine. With the vapor of methyl chloride, as pointed out in the description of the electrolysis, violent explosions occur.

Ethyl alcohol vapor at once takes fire in fluorine gas, and the liquid is decomposed with explosive violence without deposition of carbon. Aldehyde is formed to a considerable extent during the reaction.

Acetic acid and benzene are both decomposed with violence, their cold vapors burn in fluorine, and when the latter is bubbled through the liquids themselves, flashes of flame, and often most dangerous explosions, occur. In the case of benzene, carbon is deposited, and with both liquids fluorides of hydrogen and carbon are evolved. Aniline likewise takes fire in fluorine, and deposits a large quantity of carbon, which, however, if the fluorine is in excess, burns away completely to carbon tetrafluoride.

Such are the main outlines of these later researches of M. Moissan, and they cannot fail to impress those who read them with the prodigious nature of the forces associated with those minutest of entities, the chemical atoms, as exhibited at their maximum, in so far as our knowledge at present goes, in the case of the element fluorine.—Nature.

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APPARATUS FOR THE ESTIMATION OF FAT IN MILK.

By E. MOLISABI.



The author, after criticising the various methods for estimating fat in milk which have been proposed from time to time, agrees with Stokes (Analyst, 1885, p. 48), Eustace Hill (Analyst, 1891, p. 67), and Bondzynsky (Landwirth Jahrb. der Schweiz, 1889), that the method of Werner Schmid is the simplest, most rapid, and convenient hitherto introduced. The conditions tending to inaccuracy are: The employment of ether containing alcohol; boiling the mixture of milk and acid too long, when a caramel-like body is formed, soluble in ether; the difficulty of reading off the volume of ether left in the tube, owing to the gradations of the instrument being obscured by the flocculent layer of casein; when only a portion of the ether is used, fat may be left behind in the acid mixture, as shown by Allen (Chem. Zeit., 1891, p. 331). The author believes that by the invention of the simple apparatus represented in the accompanying figure, he has rendered the process both accurate and convenient. This consists of a flask B of about 75 c.c. capacity, which has a glass tap fused on, with two capillary tubes attached, the one passing upward, the other downward. The neck of flask B is ground into the neck of flask A, which holds about 90 c.c. Either of the flasks can be placed in communication with the external air by the opening a. The ether must be previously washed with one or two tenths of its volume of water, to remove traces of alcohol. The operation is performed as follows: 10 c.c. of well mixed milk are weighed in (or measured into) flask A, 10 c.c. of hydrochloric acid added, and the mixture heated to boiling on an asbestos sheet. The boiling must not exceed a minute and a half, the fluid being shaken from time to time, and not allowed to become of a deeper color than a dark brown [not black]. The flask is cooled, and 25 c.c. of ether added. The two flasks are connected as shown in the figure, the tap closed, and the whole shaken for a few minutes, the flask being vented two or three times by the opening a. The apparatus is now inverted, allowed to stand five or six minutes, the tap turned, and the dark acid liquid drawn off into flask B. By a little shaking of the ether the whole of the acid liquid may be easily got into the lower flask. The apparatus is again inverted, then separated, 10 c.c. of ether are introduced into the flask B, the tap closed, and the fluids well shaken. When the ether layer is distinct, the acid liquor is run off, and the ether solution transferred to A. The whole of the ether solution is washed in the apparatus two or three times with a little water, the flask A removed to the water bath, the ether driven off, the last traces of ether and water being removed by placing the flask in a drying oven heated from 107 to 110 deg. C., where it must remain at least twenty minutes. The usual cooling in the exsiccator and weighing concludes the operation. Examples are given showing its concordance with the Adams and other recognized processes. Sour milk, which must be weighed in the flask, can be conveniently analyzed; also cream, using 5 grammes cream and 10 c.c. hydrochloric acid. (Berichte Deutsch. Chem. Gesell., 24, p. 2204).—The Analyst.

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AMERICAN ASSOCIATION—NINTH ANNUAL REPORT OF THE COMMITTEE ON INDEXING CHEMICAL LITERATURE.[1]

[Footnote 1: From advance proof sheets of the Proceedings of the American Association for the Advancement of Science; Washington meeting, 1891.]

The Committee on Indexing Chemical Literature respectfully presents to the Chemical Section its ninth annual report.

Since our last meeting the following bibliographies have been printed:

1. A Bibliography of Geometrical Isomerism. Accompanying an address on this subject to the Chemical Section of the American Association for the Advancement of Science at Indianapolis, August, 1890, by Professor Robert B. Warder, Vice President. Proceedings A.A.A.S., vol. xxxix. Salem, 1890. 8vo.

2. A Bibliography of the Chemical Influence of Light, by Alfred Tuckerman. Smithsonian Miscellaneous Collections No. 785. Washington, D.C., 1891. Pp. 22. 8vo.

3. A Bibliography of Analytical Chemistry for the year 1890, by H. Carrington Bolton. J. Anal. Appl. Chem., v., No. 3. March, 1891.

We chronicle the publication of the following important bibliography:

4. A Guide to the Literature of Sugar. A book of reference for chemists, botanists, librarians, manufacturers and planters, with comprehensive subject index. By H. Ling Roth. London: Kegan Paul, Trench, Trubner & Co. Limited. 1890. 8vo. Pp xvi-159.

This work contains more than 1,200 titles of books, pamphlets, and papers relating to sugar. Many of the titles are supplemented with brief abstracts. The alphabetical author catalogue is followed by a chronological table and an analytical subject index. The compilation extends to the beginning of the year 1885, and the author promises a supplement and possibly an annual guide.

The ambitious work is useful but very incomplete. It does not include glucose. The author gives a list of fifteen periodicals devoted to sugar, and omits exactly fifteen more recorded in Bolton's Catalogue of Scientific and Technical Periodicals (1665-1882). Angelo Sala's Saccharologia is not named, though mentioned in Roscoe and Schorlemmer and elsewhere.

Notwithstanding some blemishes, this work is indispensable to chemists desirous of becoming familiar with the literature of sugar. It is to be hoped that a second edition brought down to date may be issued by the author.

5. A Bibliography of Ptomaines accompanies Professor Victor C. Vaughan's work, Ptomaines and Leucomaines. Philadelphia, 1888. (Pages 296-814.) 8vo.

Chemists will hail with pleasure the announcement that a new dictionary of solubilities is in progress by a competent hand. Professor Arthur M. Comey, of Tufts College, College Hill, Mass., writes that the work he has undertaken will be as complete as possible. "The very old matter which forms so large a part of Storer's Dictionary will be referred to, and in important cases fully given. Abbreviations will be freely used and formulae will be given instead of the chemical names of substances, in the body of the book. This is found to be absolutely necessary in order to bring the work into a convenient size for use ..., The arrangement will be strictly alphabetical. References to original papers will be given in all cases ..."

Professor Comey estimates his work will contain over 70,000 entries, and will make a volume of 1,500-1,700 pages.

The following letter from Mr. Howard L. Prince, Librarian of the United States Patent Office, explains itself:

WASHINGTON, D.C., February 11, 1891

Dr. H Carrington Bolton. University Club, New York, N.Y.:

DEAR SIR—In response to your request I take pleasure in giving you the following information regarding the past accomplishments and plans for the future of the Scientific Library in the matter of technological indexing.

The work of indexing periodicals has been carried on in the library for some years in a somewhat desultory fashion, taking up one journal after another, the object being, apparently, more to supply clerks with work than the pursuance of any well defined plan. However, one important work has been substantially completed, viz., a general index to the whole set of the SCIENTIFIC AMERICAN and SUPPLEMENT from 1846 to date.

It is unnecessary for me to point out to you the importance of this work, embracing a collection which has held the leading place in the line of general information on invention and progress, the labor of compiling which has been so formidable that no movement in that direction has been attempted by the publishers except in regard to the SUPPLEMENT only, and that very imperfectly. This index embraces now 184,600 cards, not punched, and at present stored in shallow drawers and fastened by rubber bands, and of course they are at present unavailable for use. There is little prospect of printing this index, and I have been endeavoring for some time to throw the index open to the public by punching the cards and fastening them with guard rods, but as yet have made no perceptible impression upon the authorities, although the expense of preparation would be only about $70.

There has also been completed an index to the English journal Engineering, comprising 84,000 cards, from the beginning to date.

An index to Dingler's Polytechnisches Journal was also commenced as long ago as 1878, carried on for six or seven years and then dropped. I hope, however, at no remote date, to bring this forward to the present time.

On taking charge of the library I was at once impressed with the immense value of the periodical literature on our shelves and the great importance of making it more readily accessible, and have had in contemplation for some time the beginning of a card index to all our periodicals on the same general plan as that of Rieth's Repertorium. I have, however, been unable to obtain sufficient force to cover the whole ground, but have selected about one hundred and fifty journals, notably those upon the subjects of chemistry, electricity and engineering, both in English and foreign languages, the indexing of which has been in progress since the first of January. This number includes substantially all the valuable material in our possession in the English language, not only journals, but transactions of societies, all the electrical journals and nearly all the chemical in foreign languages. This index will be kept open to the public as soon as sufficient material has accumulated. In general plan it will be alphabetical, following nearly the arrangement of the periodical portion of the surgeon general's catalogue. I shall depart from the strictly alphabetical plan sufficiently to group under such important subjects as chemistry, electricity, engineering, railroads, etc., all the subdivisions of the art, so that the electrical investigator, for instance, will not be obliged to travel from one end of the alphabet to the other to find the divisions of generators, conductors, dynamos, telephones, telegraphs, etc., and in the grouping of the classes of applied science the office classification of inventions will, as a rule, be adhered to, the subdivisions being, of course, arranged in alphabetical order under their general head and the title of the several articles also arranged alphabetically by authors or principal words.

With many thanks for the kind interest and valuable information afforded me, I remain, very truly yours,

HOWARD L. PRINCE, Librarian Scientific Library.

The committee much prefers to record completed work than to mention projects, as the latter sometimes fail. It is satisfactory, however, to announce that the indefatigable indexer, Dr. Alfred Tuckerman, is engaged on an extensive Bibliography of Mineral Waters. The chairman of the committee expects to complete the MS. of a Select Bibliography of Chemistry during the year, visiting the chief libraries of Europe for the purpose this summer.

H. CARRINGTON BOLTON, Chairman. F.W. CLARKE, ALBERT R. LEEDS, ALEXIS A. JULIEN, JOHN W. LANGLEY, ALBERT B. PRESCOTT.

[Dr. Alfred Tuckerman was added to the committee at the Washington meeting to fill a vacancy.]

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THE FRENCH WINE LAW.

The French wine law (Journ. Officiel, July 11, 1891) includes the following provisions:

Sect. 1. The product of fermentation of the husks of grapes from which the must has been extracted with water, with or without the addition of sugar, or mixed with wine in whatever proportion, may only be sold, or offered for sale, under the name of husk wine or sugared wine.

Sect. 2. The addition of the following substances to wine, husk wine, sugared wine, or raisin wine will be considered an adulteration:

1. Coloring matters of all descriptions.

2. Sulphuric, nitric, hydrochloric, salicylic, boric acid, or similar substances.

3. Sodium chloride beyond one gramme per liter.

Sect. 3. The sale of plastered wines, containing more than two grammes of potassium, or sodium sulphate, is prohibited.

Offenders are subject to a fine of 16 to 500 francs, or to imprisonment from six days to three months, according to circumstances.

Barrels or vessels containing plastered wine must have affixed a notice to that effect in large letters, and the books, invoices, and bills of lading must likewise bear such notice.

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THE ALLOTROPIC CONDITIONS OF SILVER.

M. Berthelot recently called the attention of the Academy (Paris) to the memoirs of Carey Lea on the allotropic states of silver, and exhibited specimens of the color of gold and others of a purple color sent him by the author. He explained the importance of these results, which remind us of the work of the ancient alchemists, but he reserved the question whether these substances are really isomeric states of silver or complex and condensed compounds, sharing the properties of the element which constituted the principal mass (97-98 per cent.), conformably to the facts known in the history of the various carbons, of the derivatives of red phosphorus, and especially of the varieties of iron and steel. Between these condensed compounds and the pure elements the continuous transition of the physical and chemical properties is often effected by insensible degrees, by a mixture of definite compounds.

The following letter appears in a recent number of the Chemical News.

Sir: In a recently published lecture, Mr. Meldola seems to call in question the existence of allotropic silver. This opinion does not appear, however, to be based on any adequate study of the subject, but to be somewhat conjectural in its nature. No experimental support of any sort is given, and the only argument offered (if such it can be called) is that this altered form of silver is analogous to that of metals whose properties have been greatly changed by being alloyed with small quantities of other metals. Does, then, Mr. Meldola suppose that a silver alloy can be formed by precipitating silver in the presence of another metal from an aqueous solution, or that one can argue from alloys, which are solutions, to molecular compounds or lakes? Moreover, he has overlooked the fact that allotropic silver can be obtained in the absence of any metal with which silver is capable of combining, as in the case of its formation by the action of soda and dextrine. Silver cannot be alloyed with sodium.

Mr. Meldola cites Prange as having shown that allotropic silver obtained with the aid of ferrous citrate contains traces of iron, a fact which was published by me several years earlier, with an analytical determination of the amount of iron found. Mr. Prange repeated and confirmed this fact of the presence of iron (in this particular case), and my other observations generally, and was fully convinced of the existence of both soluble and insoluble allotropic silver. Mr. Meldola's quotation of Mr. Prange would not convey this impression to the reader.

Of the many forms of allotropic silver, two of the best marked are the blue and the yellow.

Blue allotropic silver is formed in many reactions with the aid of many wholly different reagents. To suppose that each of these many substances is capable of uniting in minute quantity with silver to produce in all cases an identical result, the same product with identical color and properties, would be an absurdity.

Gold-colored allotropic silver in thin films is converted by the slightest pressure to normal silver. A glass rod drawn over it with a gentle pressure leaves a gray line behind it of ordinary silver. If the film is then plunged into solution of potassium ferricyanide it becomes red or blue, while the lines traced show by their different reaction that they consist of ordinary silver. Heat, electricity, and contact with strong acids produce a similar change to ordinary gray silver.

These reactions afford the clearest proof that the silver is in an allotropic form. To account for them on suppositions like Mr. Meldola's would involve an exceedingly forced interpretation, such as no one who carefully repeated my work could possibly entertain.

I am, etc.,

M. CAREY LEA. Philadelphia, October 22, 1891.

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THE SCIENTIFIC AMERICAN

Architects and Builders Edition.

$2.50 a Year. Single Copies, 25 cts.

This is a Special Edition of the SCIENTIFIC AMERICAN, issued monthly—on the first day of the month. Each number contains about forty large quarto pages, equal to about two hundred ordinary book pages, forming, practically, a large and splendid MAGAZINE OF ARCHITECTURE, richly adorned with elegant plates in colors and with fine engravings, illustrating the most interesting examples of modern Architectural Construction and allied subjects.

A special feature is the presentation in each number of a variety of the latest and best plans for private residences, city and country, including those of very moderate cost as well as the more expensive. Drawings in perspective and in color are given, together with full Plans, Specifications, Costs, Bills of Estimate, and Sheets of Details.

No other building paper contains so many plans, details, and specifications regularly presented as the SCIENTIFIC AMERICAN. Hundreds of dwellings have already been erected on the various plans we have issued during the past year, and many others are in process of construction.

Architects, Builders, and Owners will find this work valuable in furnishing fresh and useful suggestions. All who contemplate building or improving homes, or erecting structures of any kind, have before them in this work an almost endless series of the latest and best examples from which to make selections, thus saving time and money.

Many other subjects, including Sewerage, Piping, Lighting, Warming, Ventilating, Decorating, Laying out of Grounds, etc., are illustrated. An extensive Compendium of Manufacturers' Announcements is also given, in which the most reliable and approved Building Materials, Goods, Machines, Tools, and Appliances are described and illustrated, with addresses of the makers, etc.

The fullness, richness, cheapness, and convenience of this work have won for it the LARGEST CIRCULATION of any Architectural publication in the world.

A Catalogue of valuable books on Architecture, Building, Carpentry, Masonry, Heating, Warming, Lighting, Ventilation, and all branches of industry pertaining to the art of Building, is supplied free of charge, sent to any address.

MUNN & CO., PUBLISHERS, 361 BROADWAY, NEW YORK.

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THE SCIENTIFIC AMERICAN

Cyclopedia of Receipts,

NOTES AND QUERIES.

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650 PAGES. PRICE $5.

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This splendid work contains a careful compilation of the most useful Receipts and Replies given in the Notes and Queries of correspondents as published in the SCIENTIFIC AMERICAN during nearly half a century past; together with many valuable and important additions.

OVER TWELVE THOUSAND selected receipts are here collected; Nearly every branch of the useful arts being represented. It is by far the most comprehensive volume of the kind ever placed before the public.

The work may be regarded as the product of the studies and practical experience of the ablest chemists and workers in all parts of the world; the information given being of the highest value, arranged and condensed in concise form, convenient for ready use.

Almost every inquiry that can be thought of, relating to formulae used in the various manufacturing industries, will here be found answered.

Instructions for working many different processes in the arts are given. How to make and prepare many different articles and goods are set forth.

Those who are engaged in any branch of industry probably will find in this book much that is of practical value in their respective callings.

Those who are in search of independent business or employment, relating to the manufacture and sale of useful articles, will find in it hundreds of most excellent suggestions.

MUNN & CO., PUBLISHERS, 361 BROADWAY, NEW YORK.

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THE SCIENTIFIC AMERICAN SUPPLEMENT.

PUBLISHED WEEKLY.

Terms of Subscription, $5 a year.

Sent by mail, postage prepaid, to subscribers in any part of the United States or Canada. Six dollars a year, sent, prepaid, to any foreign country.

All the back numbers of THE SUPPLEMENT, from the commencement, January 1, 1876, can be had. Price, 10 cents each.

All the back volumes of THE SUPPLEMENT can likewise be supplied. Two volumes are issued yearly. Price of each volume, $2.50 stitched in paper, or $3.50 bound in stiff covers.

COMBINED RATES.—One copy of SCIENTIFIC AMERICAN and one copy of SCIENTIFIC AMERICAN SUPPLEMENT, one year, postpaid, $7.00.

A liberal discount to booksellers, news agents, and canvassers.

MUNN & CO., PUBLISHERS, 361 BROADWAY, NEW YORK, N.Y.

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A New Catalogue of Valuable Papers

Contained in SCIENTIFIC AMERICAN SUPPLEMENT during the past ten years, sent free of charge to any address. MUNN & CO., 361 Broadway, New York.

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Useful Engineering Books

Manufacturers, Agriculturists, Chemists, Engineers, Mechanics, Builders, men of leisure, and professional men, of all classes, need good books in the line of their respective callings. Our post office department permits the transmission of books through the mails at very small cost. A comprehensive catalogue of useful books by different authors, on more than fifty different subjects, has recently been published, for free circulation, at the office of this paper. Subjects classified with names of author. Persons desiring a copy have only to ask for it, and it will be mailed to them. Address,

MUNN & CO., 361 BROADWAY, NEW YORK.

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PATENTS!

Messrs. MUNN & CO., in connection with the publication of the SCIENTIFIC AMERICAN, continue to examine improvements, and to act as Solicitors of Patents for Inventors.

In this line of business they have had forty-five years' experience, and now have unequaled facilities for the preparation of Patent Drawings, Specifications, and the prosecution of Applications for Patents in the United States, Canada, and Foreign Countries. Messrs. Munn & Co. also attend to the preparation of Caveats, Copyrights for Books, Labels, Reissues, Assignments, and Reports on Infringements of Patents. All business intrusted to them is done with special care and promptness, on very reasonable terms.

A pamphlet sent free of charge, on application, containing full information about Patents and how to procure them; directions concerning Labels, Copyrights, Designs, Patents, Appeals, Reissues, Infringements, Assignments, Rejected Cases. Hints on the Sale of Patents, etc.

We also send, free of charge, a Synopsis of Foreign Patent Laws, showing the cost and method of securing patents in all the principal countries of the world.

MUNN & CO., SOLICITORS OF PATENTS, 361 Broadway, New York.

BRANCH OFFICES.—No. 622 and 624 F Street, Pacific Building, near 7th Street, Washington, D.C.

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