1. A physiological regimen comprising four to five ounces of nitrogenous principles as derived from eight to ten ounces animal muscle and albuminates; three to six ounces of fat; eight to ten ounces of hydrocarbons as yielded by ten to twelve ounces of sugar or starch food.

These proportions to be modified in such manner that the musculo-albuminates shall not sensibly exceed the normal ratio, for meat in excess itself furnishes fat during transformation. The fatty substances of easy digestion may, without inconvenience, be utilized in doses of two to three ounces. The hydrocarbons should be reduced to a minimum. As for the herbaceous elements, they contain nothing nutritive.

2. Beverage, far from being suppressed, should be augmented, in order to facilitate stomachal digestion and promote general nutrition, though alcoholic liquids must be inhibited; likewise mineral waters, except, perhaps, for occasional use. Both should be replaced by infusions of coffee or tea, taken as hot as can be drank.

Henrich Kisch insists that any method which promises rapid and marked decrease of adipose must, per se, be objectionable, even if not positively injurious, since it tends to provoke general troubles of nutrition. He suggests that first the fats and hydrocarbons be reduced as little as possible; that a moderate mixed regimen is required, containing a preponderance of albumen, small quantities of hydrocarbons and gelatinous matters, with but very little fat. Certain fatty meats, however, should be generally interdicted, such as pork sausage, smoked beef tongue, goose breast, smoked ham, fat salmon, and herring in any form. Eggs, however, may be partaken of in moderation, giving preference to the albumen over the yelk. Farinaceous foods, in the main, should be rejected, even bread being allowed only in small quantities, and then preferably in the form of toast. Cheese likewise contains too much fat; and mushrooms are so rich in hydrocarbons that they should be rejected. Condiments, water, vegetable acids (vinegars excepted) may be permitted; especially pernicious is vinegar where there is any tendency to gout or gravel. All fatty beverages—bouillon, unskimmed milk, chocolate, or cacao—and all alcoholics, are hurtful; breakfast tea is undoubtedly the best beverage, but, after a little, is advantageously replaced by light white wine diluted with water.

Kisch believes in a free and abundant use of water by the obese, especially where there is a tendency to plethora, since this fluid facilitates oxidation as the result of absorption; thus he advocates the inhibition of large quantities of cold water by all, save those presenting evidence of cardiac insufficiency. In short, his regimen is based upon the administration of a large quantity of albumen, like that of Harvey-Banting.

E. Munk recommends an almost identical dietary, save that he prefers great moderation in fluids employed as beverage.

M. Robin has sought to harmonize the opposing views regarding fluids, and therefore declares obesity arises from two distinct sources: 1. Augmentation of assimilation. 2. Reduced disassimilation. In the former, he insists water must be interdicted, while in the latter it may be allowed ad libitum.

Again, in order to recognize the exact variety of obesity, he divides his patients into three classes, each recognizable by the volume of urea excreted. In the first there is an increase above normal; in the second the volume of urea is stationary; in the third decreased, increased, or stationary.

When the urea is stationary, which is most frequently the case, it is necessary to calculate the coefficient of oxidation; that is, the relation existing between the solid matters of the urine and the urea. The elevation of the coefficient is prima facie evidence the obesity is due to excess of assimilation, while depression of the coefficient indicates default of assimilation. In the first case, water and liquids must be denied as far as possible, the same as if there was no augmentation of urea; in the second, the same as if there was diminution of urea, the patients may be permitted to imbibe fluids at pleasure.

For the obese from default of disassimilation, Robin recommends a regimen of green vegetables and bread chiefly—the latter in small quantities, however, and fluids as may be desired. By this means, on one occasion, he was able in the course of one month to diminish the weight of a female patient by twelve and a half pounds, her measurement around the waist at the same time decreasing 5.2 inches and across the stomach 4.8 inches.

M. De St. Germain achieved good results by combining judicious exercise with moderate alimentation, excluding wine and bread.

M. Dujardin Beaumetz, who professes to have given most close and careful study and attention to regimen for the obese, outlines the following, provided there is no evidence of fatty degeneration of heart.

Breakfast (at 8 a. m.)—Three-fourths of an ounce of bread "en flute"—that is abounding with crust; one and a half ounces of cold meat, ham or beef, six ounces weak black tea, sans sugar.

Lunch (at 1 p.m.)—An ounce and a half to two ounces of bread, or a ragout, or two eggs; three ounces green vegetables; one-half ounce of cheese; fruits at discretion.

Dinner (at 7 p.m.)—An ounce and a half to two ounces of bread; three to four ounces of meat, or ragout; ditto of green vegetables, salad, half an ounce of cheese, fruit ad libitum.

At meal times the patient may take only a "glass and a half" of liquid—approximately ten ounces—though a greater amount may be permitted if he abstains during the intervals.

Special alimentary regimen, however, does not constitute the sole treatment of obesity. Concurrently must be employed a number of practical adjuvants which are oftentimes of the utmost assistance. For one thing, exercise is indispensable; all authorities agree on this point. The exercise taken in the gymnasium is one of the best, notably the "wall exercise," which is more particularly suited to those afflicted with pendulous and protuberant abdomens as the result of feebleness of the hypogastric muscles, to accumulation of fat under the skin and in the omentum, and to dilation of the stomach and intestines. In the "wall exercise," the patient stands erect against an absolutely straight and plumb wall, lifts his hands (carrying a weight) straight over the head, and causes them to describe a semicircle forward. Zantz particularly insists upon arm and leg exercise for the obese, especially the former, since with the same amount of effort a larger amount of oxygen is consumed than is possible by the latter.

However, of whatever character, the exercise should be continued to the point of fatigue or dyspnoea—three thousand movements daily, gradually increased to twenty-five thousand, if the system can bear it; and under such conditions, not only is there consumption of hydrocarbons, but there is provided a veritable greed for air that augments waste. The experiments of Oertel indicate that loss of weight due to fatiguing exercise arises more particularly from dehydration, which is made good by absorption of the fluids employed as beverage; the fluids are claimed by Germain See to act as accelerants of oxidation.

During exercise there is obviously more abundant absorption of oxygen, and consequently greater elimination of carbonic acid, and as a consequence (as shown by researches of Voit), the reserve fat of the economy is attacked and diminished; in intense labor there is an average hourly consumption of about 8.2 percent. of fat. Further physical activity is useful in exercising the voluntary muscles, and thus opposing the invasion by interstitial fat of the muscle fibrils. Extreme exercise also, to a certain degree, exerts a favorable influence on the cardiac muscle, augmenting both its nutrition and its capacity for labor. With the anaemic obese, however, it is necessary to be most circumspect in prescribing forced exercise; also with the elderly obese possessed of enfeebled or fatty heart.

Hydrotherapy, especially in the form of cold douches, particularly when combined with massage, is often of considerable value in relieving obesity; the method of Harmman, of St. Germain, which has in many instances induced rapid loss of adipose, is of this class. Tepid saline baths and vapor baths have many advocates, and may afford material aid when the heart and circulation do not inhibit their employment. Hot baths elevate the temperature of the body and increase the organic exchanges, hence, as Bert and Reynard have pointed out, tend to the elimination of oxygen and carbonic acid; but when employed, the patient should be introduced while the temperature is below 130 deg. F., when it may be gradually raised in the course of thirty or forty minutes to 140 deg. F.

It has already been intimated, the chief feature of the treatment of obesity is acceleration of the exchanges; and this is in the main true, though it must also be borne in mind that, while there are obese who excrete little urea and have a depressed central nervous temperature, many may be azoturic, and besides eliminate phosphate in excess, when an oxidating treatment will not only fail, but prove positively injurious.

The bile throws out fat, therefore, to accelerate nutritive oxidations, the liver and nervous system must be acted upon, i.e., stimulated. Everything that tends to diminish the activity of the former, or depress the latter, must be avoided. Hence intellectual labor should be encouraged, or in lieu thereof, travel advised. Exercise should be taken chiefly while fasting; the limits of sleep confined to strict necessity, and siestas after meals and during the day strictly forbidden; the skin stimulated by hydro-therapeutic measures, including massage under cold affusions, during warm salt baths, etc.

To increase the activity of the liver, salicylate of soda may often be advantageously administered for its cholagogue effect; or resort may be had to saline purgatives such as are afforded by the springs of Marienbad, Kissengen, Homburg, Carlsbad, Brides, Hunyadi, or Chatel-Guyon; and it is somewhat remarkable that while undergoing a course of these waters, there is often no appreciable change in weight or obesity, though the decrease becomes most marked almost immediately upon cessation of treatment.

Everything tending to increased or fuller respiration is to be encouraged, for the fats are thus supplied with oxygen, hastening their disintegration and consumption.

Direct medicinal treatment presents no very wide scope. Bouchard imagines lime water may be useful by accelerating nutrition, but this is problematical, since fat in emulsion or in droplets does not burn. Nevertheless, alkalies in general, alkaline carbonates, liquor potassa, soaps, etc., aid in rendering fat more soluble, and consequently more susceptible to attack. The alkaline waters, however, are much less active in obesity than the saline mineral waters, unless, as sometimes happens, there is a complication of diabetes and obesity.

Purgatives are always more or less useful, and often required to be renewed with all the regularity of habit. Then too, the iodides, especially iodide of sodium or potassium, as recommended by M. Germain See, frequently prove of excellent service by aiding elimination and facilitating the mutations.

According to Kisch, the cold mineral waters containing an abundance of sulphate of soda, like Hunyadi and Marienbad, are to be preferred to the hot mineral waters, such as Carlsbad, because of their lesser irritant action on the vascular system, and because they strongly excite diuresis through their low temperature and contained carbonic acid; Carlsbad deserves preference only when obesity is combined with uric acid calculi, or with diabetes. For very anaemic persons, however, the weak alkaline and saline waters should be selected; or they should confine themselves to chalybeate waters containing an excess of sulphate of soda. Water containing sulphate of soda is also indicated as a beverage where there are troubles of the circulatory apparatus; it is contraindicated only in accentuated arterio-sclerosis.

As a matter of fact, I find the suggestion of M. Dujardin-Beaumetz, that the obese should be divided into two groups, a most practical one, for some are strong and vigorous—great eaters, perhaps even gluttons—while others, on the contrary, are feeble and debilitated, with flesh soft and flaccid; and upon the former may be imposed all the rigors of the reducing system, while the latter must be dealt with more carefully.

In general, it must be noted, the regimen prescribed for the obese is insufficient, as the following table prepared by M.C. Paul abundantly proves:

-+ + + - Author. Albuminous Fatty Matters. Matters. Hydrocarbons. -+ + + - Voit. 118 40 150 Harvey-Banting. 170 10 80 Ebstein. 100 85 50 Oertel. 155-179 25-41 70-110 Kisch (plethoric). 160 10 80 " (anaemic). 200 12 100 Normal ration. 124 55 455 -+ + + -

There is, therefore, as Dujardin-Beaumetz asserts, autophagia in the obese, and all these varieties of treatment have but one end, viz.: Reduction of the daily ration. But the quantity of nourishment should not be too greatly curtailed, for, manifestly, if the fat disappears the more surely, the muscles (rich in albumen) undergo too rapid modification. It is progressive action that should always be sought.

The quantity of aliment may be reduced either by imposing an always uniform regimen, which soon begets anorexia and disgust, or by withholding from the food a considerable quantity of fat, or, finally, by forbidding beverage during meals. Emaciation is obtained readily enough in either way, and demands only the constant exercise of will power on the part of the patient; but unhappily, severe regimen cannot always be prescribed. When the obese patient has passed the age of forty; when the heart suffers from degeneration; or when the heart is anaemic—in all, rigorous treatment will serve to still further enfeeble the central organ of circulation, and tend to precipitate accidents that, by all means, are to be avoided. In such cases, by not treating the obesity, the days of the patient will be prolonged. In degeneration of the heart, however, the method of Ebstein may be tried; and when there is renal calculi and gouty diathesis, that of Germain See may prove satisfactory.

Paris, France.

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STILT WALKING.



Sylvain Dornon, the stilt walker of Landes, started from Paris on the 12th of last March for Moscow, and reached the end of his journey at the end of a fifty-eight days' walk. This long journey upon stilts constitutes a genuine curiosity, not only to the Russians, to whom this sort of locomotion is unknown, but also to many Frenchmen.

Walking on stilts, in fact, which was common twenty years ago in certain parts of France, is gradually tending to become a thing of the past. In the wastes of Gascony it was formerly a means of locomotion adapted to the nature of the country. The waste lands were then great level plains covered with stunted bushes and dry heath. Moreover, on account of the permeability of the subsoil, all the declivities were transformed into marshes after the slightest fall of rain.

There were no roads of any kind, and the population, relying upon sheep raising for a living, was much scattered. It was evidently in order to be able to move around under these very peculiar conditions that the shepherds devised and adopted stilts. The stilts of Landes are called, in the language of the country, tchangues, which signifies "big legs," and those who use them are called tchangues. The stilts are pieces of wood about five feet in length, provided with a shoulder and strap to support the foot. The upper part of the wood is flattened and rests against the leg, where it is held by a strong strap. The lower part, that which rests upon the earth, is enlarged and is sometimes strengthened with a sheep's bone. The Landese shepherd is provided with a staff which he uses for numerous purposes, such as a point of support for getting on to the stilts and as a crook for directing his flocks. Again, being provided with a board, the staff constitutes a comfortable seat adapted to the height of the stilts. Resting in this manner, the shepherd seems to be upon a gigantic tripod. When he stops he knits or he spins with the distaff thrust in his girdle. His usual costume consists of a sort of jacket without sleeves, made of sheep skin, of canvas gaiters, and of a drugget cloak. His head gear consists of a beret or a large hat. This accouterment was formerly completed by a gun to defend the flock against wolves, and a stove for preparing meals.

The aspect of the Landeses is doubtless most picturesque, but their poverty is extreme. They are generally spare and sickly, they are poorly fed and are preyed upon by fever. Mounted on their stilts, the shepherds of Landes drive their flocks across the wastes, going through bushes, brush and pools of water, and traversing marshes with safety, without having to seek roads or beaten footpaths. Moreover, this elevation permits them to easily watch their sheep, which are often scattered over a wide surface. In the morning the shepherd, in order to get on his stilts, mounts by a ladder or seats himself upon the sill of a window, or else climbs upon the mantel of a large chimney. Even in a flat country, being seated upon the ground, and having fixed his stilts, he easily rises with the aid of his staff. To persons accustomed to walking on foot, it is evident that locomotion upon stilts would be somewhat appalling.

One may judge by what results from the fall of a pedestrian what danger may result from a fall from a pair of stilts. But the shepherds of Landes, accustomed from their childhood to this sort of exercise, acquire an extraordinary freedom and skill therein. The tchangue knows very well how to preserve his equilibrium; he walks with great strides, stands upright, runs with agility, or executes a few feats of true acrobatism, such as picking up a pebble from the ground, plucking a flower, simulating a fall and quickly rising, running on one foot, etc.

The speed that the stilt walkers attain is easily explained. Although the angle of the legs at every step is less than that of ordinary walking with the feet on the ground, the sides prolonged by the stilts are five or six feet apart at the base. It will be seen that with steps of such a length, distances must be rapidly covered.

When, in 1808, the Empress Josephine went to Bayonne to rejoin Napoleon I, who resided there by reason of the affairs of Spain, the municipality sent an escort of young Landese stilt walkers to meet her. On the return, these followed the carriages with the greatest facility, although the horses went at a full trot.

During the stay of the empress, the shepherds, mounted upon their stilts, much amused the ladies of the court, who took delight in making them race, or in throwing money upon the ground and seeing several of them go for it at once, the result being a scramble and a skillful and cunning onset, often accompanied with falls.

Up to recent years scarcely any merry-makings occurred in the villages of Gascony that were not accompanied with stilt races. The prizes usually consisted of a gun, a sheep, a cock, etc. The young people vied with each other in speed and agility, and plucky young girls often took part in the contests.

Some of the municipalities of the environs of Bayonne and Biarritz still organize stilt races, at the period of the influx of travelers; but the latter claim that the stiltsmen thus presented are not genuine Landese shepherds, but simple supernumeraries recruited at hazard, and in most cases from among strolling acrobats. The stilt walkers of Landes not only attain a great speed, but are capable of traveling long distances without appreciable fatigue.

Formerly, on the market days at Bayonne and Bordeaux, long files of peasants were seen coming in on stilts, and, although they were loaded with bags and baskets, they came from the villages situated at 10, 15, or 20 leagues distance. To-day the sight of a stilt walker is a curiosity almost as great at Bordeaux as at Paris. The peasant of Landes now comes to the city in a wagon or even by railway.—La Nature.

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REMAINS OF A ROMAN VILLA IN ENGLAND.

A correspondent of the Lincolnshire Chronicle writes: For some weeks past, remains of a Roman villa have been exposed to view by Mr. Ramsden's miners in Greetwell Fields. From, the extent of the tesselated pavements laid bare there is hardly any doubt that in the Greetwell Fields, in centuries long gone by, there stood a Roman mansion, which for magnitude was perhaps unrivaled in England. Six years ago I drew attention to it. The digging for iron ore soon after this was brought to a standstill by the company, which at the time was working the mines, ceasing their operations. Then the property came into other hands, and since then more extensive basement floors of the villa have from time to time been laid bare, and from tentative explorations which have been just made, still more floors remain to be uncovered which may be of a most interesting and instructive character. What a pity it is that the inhabitants of Lincoln have not made an effort to preserve these precious relics of the grandeur of the Roman occupation, an occupation to which England owes so much. From the Romans the people of this country inherit the sturdy self-reliance and perseverance in action which have helped to make England what it is, and from the Romans too, in a great degree, does England also inherit her colonizing instincts, which impel her people to cover the waste places of the world with colonies. If the Roman remains which have been so abundantly discovered of late years in Lincoln and its vicinity had been collected and laid out for exhibition, they would have formed a most interesting collection of antiquities worthy of the town, and well worth showing to visitors who now annually make Lincoln a visitation. Although these relics of a remote age are being dug up and are being destroyed, it is not the fault of Mr. Ramsden, for he not only preserved them as long as he conveniently could, but he also had the soil removed from over them, and had them thoroughly washed, in order that people might have an opportunity of seeing their extent and beauty. One of these patches of pavement extended 48 yards northward from what might be called the main building, which had previously been broken up. This strip was 13 ft. in breadth, and down its center ran an intricate pattern worked in blue tesserae. The pattern is much used in these days in fabrics and works of art, and is, I think, called the Grecian or Roman key pattern. On each side of this ran alternately broad ribbons of white and narrower ribbons of red tesserae. There is also another strip of pavement to the south of the preceding patch, which has been laid bare to the extent of 27 yards. This patch is about 10 ft. in breadth, and its western portion is cut up in neat patterns, which show that they formed the floors of rooms. From the eastern extremity of these floors evidently another long strip of 48 or 50 yards still remains to be uncovered. Doubtless there are other remains beneath the ground which will be laid bare as the work of mining goes on. All these floors were not deeper than from 18 to 30 inches below the surface of the soil. The bones of animals and other relics have been found in the covering soil and have been turned up by the miners from time to time. The pavement is all worked out with cubes, varying in size from an inch and a half to two inches square, each piece being placed in position with most careful exactness. The strip which extends 48 yards and is 13 ft. wide runs due north and south. There is a second patch, running east and west, and this is 27 ft. long by 10 ft. wide, while a third is 27 ft. long by 11 ft. wide, this also running in a northern direction. To the north of this latter piece, and separated only by about two feet (about the width of a wall, which very possibly was the original division), there is a strip of tesserae 16 ft. wide, which had been laid bare 40 yards. It was thought probable that at the end of the last named strip still another patch would be found. Mr. Ramsden, the manager of the Ironstone Works, is keeping a plan of the whole of the pavement, which he is coloring in exact imitation of the original work. This, when completed, will be most interesting, and he will be quite willing to show it to any one desirous of inspecting the same. Many persons have paid a visit to the spot where the discoveries have been made, and surprise is invariably expressed at the magnitude and beautiful symmetry of the work.

Several interesting fragments of Roman work have been brought to light in the course of excavations that are being made for building purposes at Twyford, near Winchester. About a month ago, a paved way, composed entirely of small red tiles, six feet in width and extending probably a considerable distance (a length of 14 ft. was uncovered), was found while digging on the site for flints. The more recent excavations are 20 ft. west of this passage, and there is now to be seen, in a very perfect state of preservation, an oven or kiln with three openings. Five yards away from this is a chamber about eight feet square, paved with tiles, and the sides coated with a reddish plaster. On one side is a ledge 15 in. from the ground, extending the whole length of the chamber; on the floor is a sunk channel with an opening at the end for the water to escape. This chamber evidently represents the bath. Portions of the dividing walls of the different chambers have also been discovered, together with various bones, teeth, horns and ornaments, but very few coins. It is probable that an alteration in the plans of the house which was about to be built on the spot will be made so as to preserve all the more interesting features of these remains in the basement. These discoveries were made at a depth of only two or three feet from the surface of the ground, and are within about a quarter of a mile of other Roman remains which were similarly brought to light a few months ago.

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[Continued from SUPPLEMENT, No. 830, page 13110.]



GUM ARABIC AND ITS MODERN SUBSTITUTES.[1]

[Footnote 1: A paper read before the Society of Chemical Industry, London, 1891. From the Journal]

BY DR. S. RIDEAL AND W.E. YOULE.

Subjoined is a table giving the absolute viscosity of various gums. A comparison of the uncorrected viscosities with the corrected shows the great importance of Slotte's correction for dextrins and inferior gum arabics; in other words, for solutions of low viscosity, while it will be observed to have little influence upon the uncorrected [eta] obtained for the Ghatti gums and the best samples of gum arabic.

TABLE OF ABSOLUTE VISCOSITIES OF 10 PER CENT. GUM AND DEXTRIN SOLUTIONS.

-+ + + Sample. [eta] [eta] Z Water Uncorrected. Corrected. = 100. -+ + + Gum arabic.......... 0.1876 0.1856 1,233 Cape gum............ 0.1575 0.1555 1,029 Indian gum.......... 0.0540 0.0470 311 Eastern gum......... 0.0689 0.0639 417 Gum arabic.......... 0.0550 0.0480 317 Senegal............. 0.0494 0.0410 271 Senegal............. 0.0468 0.0380 251 Senegal............. 0.0627 0.0557 364 Gum arabic.......... 0.0511 0.0430 285 Water............... 0.0149 0.0124 100 Ghatti.............. 0.2903 0.2880 2,322 Ghatti, 5 per cent.. 0.0903 0.0828 688 Ghatti, 5 per cent.. 0.1391 0.1350 1,089 Ghatti, 5 per cent.. 0.1795 0.1760 1,420 Ghatti, 5 per cent.. 0.1527 0.1485 1,198 Ghatti, 5 per cent.. 0.1139 0.1083 873 Ghatti, 5 per cent.. 0.1419 0.1369 1,104 Dextrin............. 0.0398 0.0255 169 Dextrin............. 0.0341 0.0196 129 Dextrin............. 0.0455 0.0380 306 Gum substitute...... 0.0318 0.0224 180 Gum substitute...... 0.0318 0.0224 180 Amrad............... 0.0793 0.0708 570 Australian.......... 0.0378 0.0283 228 Australian.......... 0.0365 0.0268 216 Brazilian........... 0.0668 0.0627 506 Brazilian........... 0.0516 0.0445 359 Ghatti.............. 0.3636 0.3621 2,920 -+ + +

In the column for [eta] corrected the differences due to the use of different instruments are of course eliminated. The absolute viscosity of water at 15 deg. C. determined in four different instruments is shown below. Poiseuille's value for water being 0.0122.

+ -+ -+ -+ -+ Instrument. 1. 2. 3. 4. + -+ -+ -+ -+ [eta] corrtd. 0.0109 0.01185 0.0124 0.0120 of water. K{1} value.. 0.000000898 0.000000863 0.000000932 0.00000052 K{2} value.. 0.235 0.2175 0.226 0.0204 + -+ -+ -+ -+

The above values for various gums and dextrins were obtained at a constant temperature of 15 deg. C. and are compared with water at that temperature. It is of the utmost importance that the temperature of the water surrounding the bulbs should be adjusted for each series of experiments to the temperature at which the absolute viscosity of the water was determined. As far as we have ascertained, in gum solutions there is a steady diminution in viscosity with increase of temperature until a certain temperature is reached, beyond which increase of heat does not markedly influence the viscosity, and it is possible that above this "critical point," as we may term it, the gum solutions once more begin to increase in viscosity. The temperature at which the viscosity becomes stationary varies somewhat with different gums, but broadly speaking it lies between 60 deg. C. and 90 deg. C., no gums showing any marked decrease in viscosity between 80 deg. C. and 90 deg. C.

The experiments we have made in this direction were conducted as follows. The 300 c.c. bottle containing the gum was placed in a capacious beaker full of hot water, and the viscosity instrument was also surrounded with water at the same temperature. Thermometers were suspended both in the beaker and the outer jar. The viscosity at the highest temperature obtained, about 90 deg. C., was then taken and repeated for every fall of 4 deg. C. till the water reached the temperature of the air.

The values so obtained gradually diminished with the increase of temperature. From the [eta] values obtained the Z values were calculated, using water at 15 deg. C. as a standard. From the Z values thus obtained taken as the ordinate, and the temperature of each experiment as the abscissa, curves were plotted out embodying the results, examples of which are given below. The curves yielded by three gums 2, 7, and 8 changed between 90 deg. C and 100 deg. C., while gum sample 4 has a curve bending between 60 deg. C. and 70 deg. C. Experimentally this increase of viscosity of the latter gum above 60 deg. C. was confirmed, but the critical point of the other solutions tried approaches too nearly to the boiling point of water for experiments to be conducted with accuracy, as the temperature of the bulbs diminishes sensibly while the experiment is being made.

If viscosity values have been determined it is possible to calculate the remaining or intermediate values for Z at any particular temperature from the general equation—

Zt = A + Bt + Ct squared

As an example of the mode of calculation we may quote the following. A gum gave the following values for Z at the temperature stated:

Gum. 50 deg. C. Z_{50 deg.} = 228

Gum. 30 deg. C. Z_{30 deg.} = 339

Gum. 20 deg. C. Z_{20 deg.} = 412

from which the constants—

A = 592.99 B = -10.2153 C = 0.0583

can be obtained, and thus the value of Z_{t deg.} for any required temperature. The numbers calculated for gums all point to a diminution in viscosity up to a certain point, and then a gradual increase. A comparison of some of the figures actually obtained in some of these experiments, compared with the calculated figures for the same temperature, shows their general agreement.



EFFECT OF TEMPERATURE UPON VISCOSITY—GUM VII.

- Temperature. [eta] Z found. Z calculated. - deg.C 50 0.0283 228 228.00 45 0.0305 246 246.55 42 0.0352 284 266.75 38 0.0368 297 289.00 34 0.0410 330 313.06 30 0.0419 339 339.00 26 0.0445 359 367.80 22 0.0492 398 396.47 20 0.0511 412 412.00 18 0.0531 428 428.00 -

EFFECT OF TEMPERATURE UPON VISCOSITY.—GUM VIII.

- Temperature. [eta] Z found. Z calculated. - deg.C. 50 0.0430 347 347 46 0.0475 383 371.14 42 0.0502 405 397.09 38 0.0510 411 424.73 34 0.0575 463 454.06 30 0.0602 485 485 26 0.0637 513 517.82 22 0.0667 538 552.25 20 0.0707 570 570 18 0.0755 609 583.07 -

The constants for the first gum are those given in the preceding column, while for the latter they were—

A = 771.9: B = -11.15: C = 0.053

As will be observed, the effect of heat appears to be the same upon the two typical gum arabics quoted above, an increase of temperature from 18 deg. C. to 50 deg. C. decreasing the viscosity by nearly one half in both cases, and the same seems to be true of most gum arabics. Roughly also the same holds good for Ghattis, as the following numbers show:

+ -+ Gum. Z at 18 deg. C. Z at 50 deg. C. + -+ Gum arabic. 1016 579 Gum arabic. 428 228 Gum arabic. 609 347 Gum arabic. 581 258 Ghatti. 572 306 Ghatti. 782 418 -+

The following table shows the effect of heat upon the viscosity of a typical Ghatti:

GHATTI GUM NO. 15.—VISCOSITY.

+ + - Temperature. [eta] Z. + + - deg.C. 50 0.0517 418 46 0.0581 468 42 0.0628 506 38 0.0726 585 34 0.0788 635 30 0.0857 691 26 0.0889 717 22 0.0919 741 20 0.0946 763 18 0.0964 777 + + -+

There is therefore no essential difference in the behavior of a Ghatti and a gum arabic on heating. Some interesting results, however, were obtained by heating gums, both Ghattis and arabics, at a fixed temperature for the same time, cooling, and then after making the solutions up to the original volume taking their viscosities at the ordinary temperature. The effect of heating for two hours to 60 deg. C., 80 deg. C., or 100 deg. C. was a small permanent alteration in viscosity of the solution, and it would therefore seem desirable that gum solutions should be made up cold to get the maximum results. The following numbers illustrate this change, viz.:

- -+ After heating to Gum Arabic Without -+ - - 10 Per Cent. heat. 60 deg.C. 80 deg.C. 100 deg.C - - - -+ Z at 18 deg.C 570 468 470 517 Z at 30 deg.C 485 400 422 439 Z at 50 deg.C 347 287 258 301 Ghatti gum No. 15, 5 per cent. Z at 18 deg.C. 1,104 780 660 758 + - - - -

The variation of viscosity with strength of solution was also studied with one or two typical gums. A 10 per cent. is invariably more than twice as viscous as a 5 per cent. solution. The following curve was obtained from one of the Ghattis. Similar results were shown by other gums.



It would seem, therefore, that strong solutions, say of 50 per cent. strength, would be more alike in viscosity than solutions of 5 per cent. strength of the same gums. In other words, the viscosity of a gum solution should be taken as nearly as possible to the strength it is used at, to obtain an exact quantitative idea of its gumming value.

The observation of this fact was one of the circumstances which decided us to use 5 per cent. solutions for the determination of Ghatti gum viscosities, the ratio between the 5 per cent. and 10 per cent. solutions of gum arabics being roughly the same as that between the respective weights required for gumming solutions of equal value.

From observation of the general nature of the solutions of Ghatti gums, and from the fact that when allowed to stand portions of the apparently insoluble matter passed into solution, the hypothesis suggested itself that metarabin was soluble in arabin, although insoluble in cold water. If this hypothesis were correct, it would explain the apparent anomaly of Ghattis giving solutions of higher viscosity than gum arabics, although they leave insoluble matter behind. The increase in viscosity would be due to the thickening of the arabic acid by the metarabin. Moreover, the solutions yielded by various Ghattis leaving insoluble matter behind would be all of the same kind, viz., a saturated solution of metarabin in arabin more or less diluted by water. Still further, if the insoluble residue of a Ghatti be the residual metarabin over and above that required to saturate the arabin, then it will be possible to dissolve this by the addition of more arabin in the form of ordinary gum arabic. In order to see if this were the case the following experiments were performed. Equal parts of a Ghatti and of a gum arabic were ground up together and dissolved in water. The resulting solution was clear. It was diluted until of 10 per cent. strength, and its viscosity then taken:

-+ -+ + Contains 50 per Cent. Ghatti. -+ -+ + A. Pressure 200 mm [eta] Z. Temperature 15 deg. C 0.2517 2,030 -+ -+ +

The viscosity of this solution therefore was considerably greater than the mean viscosity of the 10 per cent. solutions of the Ghatti and the gum arabic, viz., (0.288 + 0.0636)/2 = 0.1758 for the calculated [eta]. Hence it is evident that the increase in viscosity is due to the solution of the metarabin.

Next a solution was made from a mixture of 70 per cent. Ghatti and 30 per cent. gum arabic. This was also clear and gave a considerably higher viscosity than the previous solution.

- Contains 70 per Cent. Ghatti. - - + B. Pressure 200 mm [eta] Z. Temperature 15 deg. C 0.3177 2,562 -+ -

It will be obvious that the increase of viscosity over the previous solution in this case must be due to the smaller amount of the thin gum arabic which is present, i.e., in the first case there is more gum arabic than is required to dissolve the whole of the insoluble metarabin. Further experiments showed that this is also true of the second mixture, as the viscosities of the following mixtures illustrate:

- -+ Strength of Solution. [eta] Z. -+ - C. 80 per cent. Ghatti. 0.3642 2,937 D. 75 per cent. Ghatti. 0.33095 2,669 E. 77.5 per cent. Ghatti. 0.4860 3,819 - -

This last solution E we called for convenience the "maximum viscosity" solution, as we believe it to be a 10 per cent. solution containing arabin very nearly saturated with metarabin. As will be observed, its viscosity differs widely from those of solutions C and D, between which it lies in percentage of Ghatti. The first named solution C contains too little of gum arabic to dissolve the whole of the metarabin. Consequently there is a residue left undissolved, which of course diminishes its viscosity. The second solution D is too low in viscosity, as it still contains too much of the weak gum arabic, and as will be seen further on, a very slight change in the proportions increases or decreases the viscosity enormously.

We next tried a series of similar experiments with a Ghatti containing far less insoluble residue and which consequently would require less gum arabic to produce a perfect solution. Mixtures were made in the following proportions, viz.:

+ + -+ - 13.3 per Cent. Ghatti. + + -+ F. Pressure 200 mm. [eta] Z. Temperature 15 deg. C. 0.0976 787 + + -+

+ + -+ - 86.6 per Cent. Ghatti. + + -+ G. Pressure 200 mm. [eta] Z. Temperature 15 deg. C. 0.4336 3,497 + + -+

This latter solution is approaching fairly closely to our "maximum viscosity" with the previous Ghatti, and probably a very slight decrease in the amount of gum arabic would bring about the required increase in viscosity.

When these experiments were first commenced we were still under the impression, which several months' experience of working with gums had produced, namely, that the Ghattis were quite distinct in their properties to ordinary gum arabics. But the new hypothesis, and the experiments undertaken to confirm it, showed clearly that if the viscosity of a gum solution depends on the ratio of metarabin to arabin, then there is no absolute line of demarkation between a Ghatti and a gum arabic. In other words, there is a constant gradation between gum arabic and Ghattis, down to such gums as cherry gum, consisting wholly of metarabin and quite insoluble in water. Therefore those gum arabics which are low in viscosity consist of nearly pure arabin, while as the viscosity increases so does the amount of metarabin, until we come to Ghattis which contain more metarabin than their arabin can hold in solution, when their viscosity goes down again.

From these observations it would follow, that by taking a gum of less viscosity than the gum arabic previously used to dissolve the Ghatti, less of it would be required to do the same work. We confirmed this suggestion experimentally by taking another gum arabic of viscosity 0.0557 at 15 deg. C. A mixture containing 93.3 per cent. of this Ghatti and 6.7 per cent. of our thinnest gum arabic gave a clear solution which had the highest viscocity we have yet obtained for a 10 per cent. solution.

-+ H. Pressure 200 mm. [eta] Z. Temperature 15 deg. C. 0.5525 4,456 + -

This gum arabic may be regarded as nearly pure arabin (as calcium and potassium, etc., salt). By diluting the new "maximum viscosity" solution, therefore, with the 10 per cent. solution of the gum arabic in fixed proportions we obtain a series of viscosities which are shown in the following curve.



Besides obtaining this curve for change in viscosity from maximum amount of metarabin to no metarabin at all, we also traced the decrease in viscosity of the "maximum" solution by dilution with water. The following numbers were thus obtained, and plotted out into a curve.

Having obtained this curve, we are now in a position to follow up the hypothesis by calculating the surplus amount of insoluble matter in a Ghatti. For, let it be conceded that the solution of any Ghatti leaving an insoluble residue is a mixture of arabin and metarabin in the same ratio as our "maximum" solution, only more diluted with water, then from the found viscosity we obtain a point on the curve for dilution, which gives the percentage of dissolved matter.

Now to show the use of this: The Z value for a 10 per cent. solution of the second Ghatti at 15 deg. C. is 2,940. This corresponds on the curve to 8.4 dissolved matter. 10 - 8.4 = 1.6 grammes in 10 grammes, which is insoluble.

CHANGE OF VISCOSITY WITH DILUTION—"MAXIMUM" SOLUTION. 15 deg. C. TEMPERATURE.

- Percentage. [eta] Z. - 10 0.55250 4,456 9 0.42850 3,456 8 0.35120 2,832 7 0.27660 2,230 6 0.22290 1,797 5 0.16810 1,355 4 0.11842 955 3 0.08020 647 2 0.06190 499 1 0.03610 291 -



We have already shown that a "maximum" viscosity solution of this gum is formed when 6.7 per cent, of thin gum arabic is added to it, and therefore 6.7 parts of a thin gum arabic are required to bring 16 parts of metarabin into solution. A convenient rule, therefore, in order to obtain complete solution of a Ghatti gum is to add half the weight in thin gum of the insoluble metarabin found from the viscosity determination. But the portion of the gum which dissolved is made up in a similar manner (being a diluted "maximum" solution).

Therefore the 84 per cent. of soluble matter contains 58 parts of metarabin, and the total metarabin in this gum is 58 + 16 = 74 per cent, on the dry gum.

With these solutions of high viscosity some other work was done which may be of interest. The temperature curves of the mixtures marked E, G, and F were obtained between 60 deg. C. and 15 deg. C. The two former curves showed a direction practically parallel to that at the 10 per cent. solutions, and as they were approaching to the "maximum" solution, this is what one would expect. Mr. S. Skinner, of Cambridge, was also good enough to determine the electrical resistances of these solutions and the Ghattis and gum arabics employed in their preparation. The electrical resistance of these gum solutions steadily diminishes as the temperature increases, and the curve is similar to those obtained for rate of change with temperature. Although the curves run in, roughly, the same direction, there does not appear to be any exact ratio between the viscosities of two gums say at 15 deg. C. and their electrical resistances at the same temperature; hence it would not seem possible to substitute a determination of the electrical resistance for the viscosity determination. The results appear to be greatly influenced by the amount of mineral matter present, gums with the greatest ash giving lower resistances.

Experiments were conducted with two Ghattis and two gum arabics, besides the mixtures marked E, F, and H. Comparison of the electrical resistances with the viscosities at 15 deg. C. shows the absence of any fixed ratio between them.

-+ + -+ Gum or deg.C. Ohms Z Viscosity Mixture. Resistance. at 15 deg. C. -+ + -+ - Ghatti, 1 10 5,667 1,490 Ghatti, 2 15 2,220 2,940 Arabic 1 15 1,350 605 Arabic 2 10 2,021 449 Mixture F 15 1,930 787 Mixture E 11.3 2,058 3,919 -+ + -+ -

While performing these experiments, an attempt was made to obtain an "ash-free" gum, in order to compare its viscosity with that of the same gum in its natural state. A gum low in ash was dissolved in water, and the solution poured on to a dialyzer, and sufficient hydrochloric acid added to convert the salts into chlorides. When the dialyzed gum solution ceased to contain any trace of chlorides, it was made up to a 10 per cent. solution, and its viscosity determined under 100 mm. pressure, giving the following results at 15 deg. C.:

- - [eta] Z - - Natural gum..... 0.05570 449 "Ash-free" gum.. 0.05431 438 - -

Thus showing that the viscosity of pure arabin is almost identical with that of its salts in gum.

The yield of furfuraldehyde by the breaking down of arabin and metarabin was thought possibly to be of some value in differentiating the natural gums from one another, but we have not succeeded in obtaining results of much value. 0.2 gramme of a gum were heated with 100 c.c. of 15 per cent. sulphuric acid for about 21/2 hours in an Erlenmeyer flask with a reflux condenser. After this period of time, further treating did not increase the amount of furfuraldehyde produced. The acid liquid, which was generally yellow in color, was then cooled and neutralized with strong caustic soda. The neutral or very faintly alkaline solution was then distilled almost to dryness, when practically the whole of the furfuraldehyde comes over. The color produced by the gum distillate with aniline acetate can now be compared with that obtained from some standard substance treated similarly. The body we have taken as a standard is the distillate from the same weight of cane sugar. The tint obtained with the standard was then compared with that yielded by the gum distillate from which the respective ratios of furfuraldehyde are obtained. The following table shows some of these results:

-+ + -+ Comparative Yield Amount of Substance. of Furfuraldehyde. Glucose Produced. -+ + -+ Cane sugar 1.00 .. Starch 0.50 .. Gum arabic 1.33 34.72 Gum arabic 1.20 43.65 Ghatti, 1 1.00 26.78 Ghatti, 2 1.33 22.86 Metarabin 1.75 .. -+ + -+

The amount of reducing sugar calculated as glucose is also appended. This was estimated in the residue left in the flask after distillation by Fehling's solution in the usual way. The yields of furfuraldehyde would appear to have no definite relation to the other chemical data about a gum, such as the potash and baryta absorptions or the sugar produced on inversion.

The action of gum solutions upon polarized light is interesting, especially in view of the fact that arabin is itself strongly laevo-rotatory [alpha]_{D} = -99 deg., while certain gums are distinctly dextro-rotatory. Hence it is evident that some other body besides arabin is present in the gum. We have determined the rotatory power of a number of gum solutions, the results of which are subjoined. On first commencing the experiments we experienced great difficulty from the nature of the solutions. Most of them are distinctly yellow in color and almost opaque to light, even in dilute solutions such as 5 percent. We found it necessary first to bleach the gums by a special process; 5 grammes of gum are dissolved in about 40 c.c. of lukewarm water, then a drop of potassium permanganate is added, and the solution is heated on a water bath with constant stirring until the permanganate is decomposed and the solution becomes brown. A drop of sodium hydrogen sulphate is now added to destroy excess of permanganate. At the same time the solution becomes perfectly colorless.

It can now be cooled down and made up to 100 c.c., yielding a 5 per cent. solution of which the rotatory power can be taken with ease. Using a 20 mm. tube and white light the above numbers were obtained.

- Gum or Dextrin. Solution used. [alpha]_{D} - Per Cent. Aden, 1 5 - 33.8 Cape, 2 5 + 28.6 Indian, 3 5 + 66.2 Eastern, 4 5 - 26.0 Eastern, 5 5 - 30.6 Senegal, 6 5 - 17.6 Senegal, 7 5 - 18.4 Senegal, 8 21/2 - 19.6 Senegal, 9 5 - 38.2 Senegal, 10 5 - 25.8 Amrad 21/2 + 57.6 Australian, 1 5 - 28.2 Australian, 2 5 - 26.4 Brazilian, 1 21/2 - 36.8 Brazilian, 2 21/2 + 21.0 Dextrin, 1 5 +148.0 Dextrin, 2 5 +133.2 Ghatti, 1 5 - 39.2 Ghatti, 2 5 - 80.4 -

These numbers do not show any marked connection between the viscosity, etc., of a gum and its specific rotatory power.

When gum arabic solution is treated with alcohol the gum is precipitated entirely if a large excess of spirit be used. With a view to seeing if the precipitate yielded by the partial precipitation of a gum solution was identical in properties to the original gum, we examined several such precipitates from various gums to ascertain their rotatory power. We found in each case that the specific rotatory power of the alcohol precipitate redissolved in water was not the same as that of the original gum. In other words these gums contained at least two bodies of different rotatory powers, of which one is more soluble in alcohol than the other. O'Sullivan obtained similar results with pure arabin. The experiments were conducted in the following manner:

(a.) Five grammes of a dextro-rotatory gum (No. 3 in table) were dissolved in 20 c.c. of water. To the solution was added 90 c.c. of 95 per cent. alcohol. The white precipitate which formed was thrown on to a tared filter and washed with 30 c.c. more alcohol. The total filtrate therefore was 140 c.c. The precipitate was dried and weighed = 2.794 grammes or 55.88 per cent. of the total gum. The precipitate was then redissolved in water, bleached as before and diluted to a 5 per cent. solution. This was then examined in the polarimeter. Readings gave the value [alpha]{D} = +58.4 deg.. The previous rotatory power of the gum was +66 deg.. Now the alcohol was driven off from the filtrate, which, allowing for the 11.95 per cent. of water in the gum, should contain 32.17 per cent. of gum. The alcohol-free liquid was then diluted to a known volume (for 5 per cent, solution), and [alpha]{J} found to be +57.7 deg.. This experiment was then repeated again, using 5 grammes of No. 3, when 3.5805 grammes of precipitate were obtained, using the same volumes of alcohol and water. The precipitate gave [alpha]{J} = +57.4 deg.; the filtrate treated as before, only the percentage of gum dissolved being directly determined instead of being calculated by difference, gave [alpha]{J} = +52.5 deg..

(b.) Another gum (No. 9) with [alpha]_{J} = -38.2 deg. and containing 13.86 per cent, of moisture, gave 2.3315 grms. of precipitate when similarly treated. The precipitate gave when redissolved in water [alpha]_{J} = -20.8 deg.. The filtrate containing 39.5 per cent, real gum gave [alpha]_{J} = -67.5 deg., so that the least laevo-rotatory gum. was precipitated by the alcohol.

The Ghattis apparently are all laevo-rotatory, and give much less alcoholic precipitates than the gum arabic. The precipitation moreover was in the opposite direction, that is, the most laevo-rotatory gum was thrown down by the alcohol. The appended table shows the nature of the precipitates and the respective amounts from two Ghattis and two gum arabics. It will be observed that the angle of rotation in three of the cases is decidedly less both for precipitate and filtrate than for the original solution:

SPECIFIC ROTATORY POWERS OF GUMS.

- -+ Gum Weight Weight Weight [alpha]_{J} [alpha]_{J} [alpha]_{J} used. Gum Alcohol Gum Original Alcohol Filtrate. Waken. Precip- Filtrate Gum. Precipitate. itate. + - - Grms. /a...... 5 2.7940 1.9415 +58.4 +53.7 3{ +66.2 ...... 5 3.5805 0.8910 +57.4 -52.5 /a...... 5 2.3315 2.3736 -20.8 -67.5 9{ -38.2 ...... 4.9620 2.3310 2.4180 -19.4 -63.4 /a. 3.4900 0.3925 2.7920 -104.2 -76.0 Ghatti{ -140.8 . 3.2450 0.4605 2.8385 -106.0 -72.4 /a. 2.2550 0.2900 1.8078 -106.04 68.0 Ghatti{ -147.05 . 2.6635 0.2845 2.3360 -102.04 -66.2 - -

The hygrometric nature of a gum or dextrin is a point of considerable importance when the material is to be used for adhesive purposes. The apparatus which we finally adopted after many trials for testing this property consists simply of a tinplate box about 1 ft. square, with two holes of 2 in. diameter bored in opposite sides. Through these holes is passed a piece of wide glass tubing 18 in. long. This is fitted with India rubber corks at each end, one single and the other double bored. Through the double bored cork goes a glass tube to a Woulffe's bottle containing warm water. A thermometer is passed into the interior of the tube by the second hole. The other stopper is connected by glass tubing to a pump, and thus draws warm air laden with moisture through the tube. Papers gummed with the gums or dextrins, etc., to be tested are placed in the tube and the warm moist air passed over them for varying periods, and their proneness to become sticky noted from time to time. By this means the gums can be classified in the order in which they succumbed to the combined influences of heat and moisture. We find that in resisting such influences any natural gum is better than a dextrin or a gum substitute containing dextrin or gelatin. The Ghattis are especially good in withstanding climatic changes.

Dextrins containing much starch are less hygroscopic than those which are nearly free from it, as the same conditions which promote the complete conversion of the starch into dextrin also favor the production of sugars, and it is to these sugars probably that commercial dextrin owes its hygroscopic nature. We have been in part able to confirm these results by a series of tests of the same gums in India, but have not yet obtained information as to their behavior in the early part of the year.

The fermentation of natural gum solutions is accompanied by a decrease in the viscosity of the liquid and the separation of a portion of the gum in lumps. Apparently those gums which contain most sugar, as indicated by their reduction of Fehling's solution, are the most susceptible to this change. Oxalic acid is formed by the fermentation, which by combination with the lime present renders the fermenting liquid turbid, and also some volatile acid, probably acetic.

We have made some experiments with a gum which readily fermented—in a week—as to the respective value of various antiseptics in retarding the fermentation. Portions of the gum solutions were mixed with small quantities of menthol, thymol, salol, and saccharin in alkaline solution, also with boric acid, sodium phosphate, and potash alum in aqueous solution. Within a week a growth appeared in a portion to which no antiseptic had been added; the others remained clear. After over five months the solutions were again examined, when the following results were observed:

+ - Antiseptics. Solution after Five Months. + - Menthol in KOH..... Some growth at bottom, upper layer clear. Thymol in KOH..... Growth at top, gum white and opaque. Salol in KOH........ Growth at top, gum black and opaque Saccharin in KOH ... White growth at top. Boric acid............ Remained clear; did not smell. Sodium phosphate ... Slight growth at top. Potash alum......... Slight growth at top. + -

The solution to which no antiseptic had been added was of course quite putrid, and gave the reactions for acetic acid.

In the earlier part of this paper we have given a short account of the chief characteristics of the more important gum substitutes. The following additional notes may be of interest.

The ashes of most gum substitutes, consisting chiefly of dextrin, are characterized by the high percentage of chlorides they contain, due no doubt to the use of hydrochloric acid in their preparation. The soluble constituents of the ash consist of neutral alkaline salts, but as a rule no alkaline carbonates, and it is thus possible to demonstrate the absence of any natural gum in such a compound. We have seldom noticed the presence of any sulphates in such ashes, but when sulphurous or sulphuric acids have been used in the starch conversion it will be found in small quantities.

We have already pointed out that the potash absorption value of a gum is low and that dextrins give high numbers, but the latter vary very considerably, and as the starch and sugar present also influence the potash absorption value, it does not give information of much service. The following table shows the kind of results obtained:

-+ + + Sample. KOH Starch. Real Gum. absorbed. -+ + + Per Cent. Per Cent. Dextrin, 1 25.40 1.99 .. Dextrin, 2 19.70 13.13 .. Dextrin, 3 7.57 24.72 .. Artificial gum, 1 19.70 10.98 9.00 Artificial gum, 2 13.70 8.05 23.50 Starch 9.43 100.00 None -+ + +

The baryta absorptions seem to be chiefly due to the quantity of starch present in the composition:

+ -+ - Sample. Starch. BaO absorbed. + - - Per Cent. Per Cent. Dextrin, 1 1.99 1.75 Dextrin, 2 13.13 3.53 Dextrin, 3 24.72 5.64 Starch 100.00 23.61 + -+ -

The viscosity of a dextrin or artificial gum is determined in exactly the same way as a natural gum, using 10 per cent. solutions. It would probably be an improvement to use 10 per cent. solutions for many of the dextrins, as they are when low in starch extremely thin.

The hygroscopic nature of dextrins renders them unsuitable for foreign work, but when the quantity of starch is appreciable, better results are obtainable. A large percentage of unaltered starch is usually accompanied with a small percentage of sugar, and no doubt this is the explanation of this fact. An admixture containing natural gum of course behaved better than when no such gum is present. Bodies like "arabol" made up with water and containing gelatin are very hygroscopic when dry, although as sold they lose water on exposure to the air. Gum substitutes consisting entirely of some form of gelatin with water, like fish glue, are also somewhat hygroscopic when dried. The behavior of these artificial gums and dextrins on exposure to a warm moist atmosphere can be determined in the same apparatus as described for gums.

The process we have adopted for estimating the glucose starch and dextrin in commercial gum substitutes is based on C. Hanofsky's method for the assay of brewers' dextrins (this Journal, 8, 561). A weighed quantity of the dextrin is dissolved in cold water, filtered from any insoluble starch, and then the glucose determined directly in the clear filtrate by Fehling's solution. The real dextrin is determined by inverting a portion of the filtered liquid with HCl, and then determining its reducing power. The starch is estimated by inverting a portion of the solid dextrin, and determining the glucose formed by Fehling. After deducting the amounts due to the original glucose and the inverted dextrin present, the residue is calculated as starch. A determination of the acidity of the solution is also made with decinormal soda, and results returned in number of c.c. alkali required to neutralize 100 grammes of the dextrin. Results we have obtained using this method are embodied in the following table:

ANALYSIS OF GUM SUBSTITUTES

+ -+ -+ + + -+ -+ - No. Glucose. Dextrin. Starch. Moisture. Gum, Ash. Acidity. &c. + -+ -+ + + -+ -+ - cc. 1 8.92 81.57 1.99 10.12 None 0.207 57.3 2 7.19 71.46 13.13 10.40 None 0.120 44.8 3 1.29 69.42 24.72 4.17 1.12 0.280 5.22 4 8.40 60.98 10.98 10.09 9.02 0.530 20.0 5 10.60 44.98 8.05 12.20 23.57 0.600 52.0 6 14.80 11.57 36.46 34.87 1.89 0.580 8.0 7 8.00 29.61 26.78 33.98 0.88 0.750 88.0 8 2.29 52.38 37.65 None 7.335 0.315 9.6 + -+ -+ + + -+ -+ -

In those cases in which the substitute is made by admixture with gelatin or liquid glue the quantity of other organic matter obtained can be checked by a Kjeldahl determination of the total nitrogen. If a natural gum is added, it will be partially converted into sugar when the filtered liquid is inverted, and so make the dextrin determination slightly too high.

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MR. CAILLETET'S CRYOGEN.

The "cryogen," a new apparatus constructed by Mr. E. Ducretet, from instructions given by Mr. Cailletet, is designed for effecting a fall of temperature of from 70 deg. to 80 deg. C. below zero, through the expansion of liquid carbonic acid.

The apparatus consists of two concentric vessels having an annular space between them of a few centimeters. A worm, S, is placed in the internal vessel R. All this is of nickel plated copper. The worm, S carries, at Ro', an expansion cock and ends, at O in the annular space, R'. A very strong tube is fixed to the cock, Ro', and to the ajutage, A'. It receives the tube, Tu, which, at the time of an experiment, is coupled with the cylinder of carbonic acid, CO squared. A tubulure, D, usually closed by a plug, Bo, communicates with the inner receptacle, R. This is capable of serving in certain experiments in condensation. The table, Ta, of the tripod receives the various vessels or bottles for the condensed products.

The entire apparatus is placed in a box, B, lined with silk waste and provided with a cover, C, of the same structure. Apertures, Th, Ro, and T", allow of the passage of a key for acting upon the cock, Ro', as well as of thermometers and stirrers if they are necessary.

When it is desired to operate, the internal vessel, R, is filled with alcohol (3 quarts for the ordinary model). This serves as a refrigerant bath for the experiments to be made. The worm, S, having been put in communication with the carbonic acid cylinder, CO squared, the cock, Ro, of the latter is turned full on. The cock of the worm, which is closed, is opened slightly. The vaporization and expansion of the liquid carbonic acid cause it to congeal in the form of snow, which distributes itself and circulates in the worm, S, and then in R. The flakes thus coming in contact with the metallic sides of S rapidly return to the gaseous state and produce an energetic refrigeration. At the lower part of the annular space, R', are placed fragments of sponge impregnated with alcohol. The snow that has traversed the worm without vaporizing reaches R'. and dissolves in this alcohol, and the refrigeration that results therefrom completes the lowering of the temperature. The gas finally escapes at O, and then through the bent tube, T".



The apparatus may be constructed with an inverse circulation, the carbonic acid then entering the annular vessel, R, directly, and afterward the worm, S, whence it escapes to the exterior of the apparatus. The expansion cock sometimes becomes obstructed by the solidification of the snow. It will then suffice to wait until the circulation becomes re-established of itself. It may be brought about by giving the cock, Ro', a few turns with the wooden handled key that serves to maneuver the latter. It is not necessary to have a large discharge of carbonic acid, and consequently the expansion cock needs to be opened but a little bit. A few minutes suffice to reduce the temperature of the alcohol bath to 70 deg., with an output of about from 41/2 to 51/2 lb. of liquid carbonic acid. When the circulation is arrested, the apparatus thus surrounded by its isolating protective jackets becomes heated again with extreme slowness. In one experiment, it was observed that at the end of nine hours the temperature of the alcohol had risen but from 70 deg. to 22 deg.. On injecting a very small quantity of liquid carbonic acid from time to time, a sensibly constant and extremely low temperature may be maintained indefinitely.—Le Genie Civil.

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METHOD OF PRODUCING ALCOHOL.

In carrying out my improved process in and with the apparatus employed in ordinary commercial distilleries, says Mr. Alfred Springer, of Cincinnati, O., I preferably employ separate vats or tubs for the nitric acid solution and the material to be treated, and a convenient arrangement is to locate the nitric acid tub directly under the grain tub, so that one may discharge into the other. In the upper vat is placed the farinaceous material, preferably ground, thoroughly steeped in three times its weight of water, and, where whole grain is used, preferably "cooked" in the ordinary manner. The vat into which the dilute acid is placed is an ordinary cooking tub of suitable material to resist the acid, provided with closed steam coils and also nozzles for the discharge of steam into the contained mass. Into this vat is placed for each one hundred parts of the grain to be treated one part of commercial nitric acid diluted with fifty parts of water and brought to a state of ebullition and agitation by the steam coils and the discharge through the nozzles, the latter being regulated so that the gain by condensation of steam approximately equals the loss by evaporation. The farinaceous contents of the upper vat are allowed to flow slowly into the nitric acid solution while the ebullition and agitation of the mass is continued. This condition is then maintained for six to eight hours, after which the mass is allowed to stand for one day or until the saccharification becomes complete. The conversion can be followed by the "iodine test" for intermediary dextrins and the "alcohol test" for dextrin. After the saccharification is complete I may partially or wholly neutralize the nitric acid, preferably with potassium or Ammonium carbonate, preferably employing only one-half the amount necessary to neutralize the original quantity of nitric acid used, so that the mass now ready to undergo fermentation has an acid reaction. The purpose in view here is to keep the peptones in solution also, because an acid medium is best adapted to the propagation of the yeast cells. It is not absolutely necessary to even partially neutralize the nitric acid, but it is preferable. Yeast is now added, and the remaining processes are similar to those generally employed in distilleries, excepting that just prior to distillation potassium carbonate sufficient to neutralize the remaining nitric acid is added, in order to avoid corrosion of the still and correct the acid reaction of the slop.

As a variant of the process I sometimes add to the usual amount of nitric acid an additional one one-hundredth part of phosphoric acid on account of its beneficial nutritive powers—that is to say, to one hundred parts of grain one part of nitric acid and one one-hundredth part of phosphoric acid.

While my improved process is based on the well-known converting power of acids on starch, I am not aware that it has ever been applied in the manner and for the purposes I have described. For example, sulphuric and hydrochloric, also sulphuric and nitric, acids have been employed in the manufacture of glucose; but in every such case the resulting products were not capable of superseding those obtained by the existing methods of saccharification used in distilleries. In my process, on the other hand, the product is so capable. Not only may malted grain be entirely omitted, but more fermentable products are formed and the products of fermentation are purer. The saccharification being more complete, there are less intermediary and nonfermentable dextrins, and the yield of spirits is therefore increased. Malted grain being omitted or used in reduced quantity, there is less lactic acid and few or foreign ferments to contaminate the fermenting mass; also, the formation of higher alcohols than the ethyl alcohol is almost totally suppressed. Consequently the final yield of spirits is purer in quality and requires little or no further purification. Also, further, the nitrates themselves acting as nutrients to the yeast cells, these become more active and require less nutrition to be taken from the grain.

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SPECTROSCOPIC DETERMINATION OF THE SENSITIVENESS OF DRY PLATES.

After describing other methods of determining the sensitiveness of plates, Mr. G.F. Williams, in the Br. Jour. of Photo., thus explains his plan. I will now explain the method I adopt to ascertain the relative sensitiveness of plates to daylight. Procure a small direct vision pocket spectroscope, having adjustable slit and sliding focus. To the front of any ordinary camera that will extend to sixteen or eighteen inches, fit a temporary front of soft pine half an inch thick, and in the center of this bore neatly with a center bit a hole of such diameter as will take the eye end of the spectroscope; unscrew the eyehole, and push the tube into the hole in wood, bushing the hole, if necessary, with a strip of black velvet glued in to make a tight fit. By fixing the smaller tube in the front of camera we can focus by sliding the outer tube thereon; if we fix the larger tube in the front, we should have to focus inside the camera, obviously most inconvenient in practice. Place the front carrying the spectroscope in situ in the camera, and rack the latter out to its full extent; point the camera toward a bright sky, or the sun itself, if you can, while you endeavor to get a good focus. The spectrum will be seen on the ground glass, probably equal in dimensions to that of a quarter plate. Proceed to focus by sliding the outer tube to and fro until the colors are quite clear and distinct, and at same time screw down the slit until the Fraunhofer lines appear. By using the direct rays of the sun, and focusing carefully, and adjusting the slit to the correct width, the lines can be got fairly sharply. Slide your front so that the spectrum falls on the ground glass in just such a position as a quarter plate glass would occupy when in the dark slide, and arrange matters so that the red comes to your left, and the violet to the right, and invariably adopt that plan. It is advisable to include the double H lines in the violet on the right hand edge of your plate. They afford an unerring point from which you can calculate backward, finding G, F, E, etc., by their relative positions to the violet lines. Otherwise you may be mistaken as to what portion of the spectrum you are really photographing. The red should just be seen along the left edge of the quarter plate. When all is arranged thus, you utilize three-fourths of your plate with the spectrum, with just a little clear glass at each end. Before disturbing the arrangement of the apparatus, it is desirable to scratch a mark on the sliding tube, and make a memorandum of the position of all the parts, so that they may be taken away and replaced exactly and thus save time in future.

To take a photograph of the spectrum, put a quarter plate in the dark slide and place in camera; point the camera toward a bright sky, or white cloud, near the sun—not at the sun, as there is considerable difficulty in keeping the direct rays exactly in the axis of the spectroscope—draw the shutter, and give, say, sixty seconds. On development, you will probably obtain a good spectrum at the first trial. The duration of exposure must, of course, depend upon the brightness of the day; but if the experiments are to have relative values, the period of exposure must be distinctly noted, and comparisons made for a normal exposure of sixty seconds, ninety seconds, two minutes or more, just according to whatever object one has in view in making the experiments. With a given exposure the results will vary with the light and the width of the slit, as well as being influenced by the character of the instrument itself. Further, all such experiments should be made with a normal developer, and development continued for a definite time. The only exception to this rule would be in the event of wishing to ascertain the utmost that could be got out of a plate, but, under ordinary circumstances, the developer ought never to vary, nor yet the duration of development. To try the effect of various developers, or varying time in development, a departure must be made of such a nature as would operate to bring out upon each plate, or piece of a plate, the utmost it would develop short of fog, against which caution must be adopted in all spectrum experiments.

On development, say for one, two, or three minutes, wash off and fix. You will recognize the H violet lines and the others to the left, and this experiment shows what is the sensitiveness of this particular plate to the various regions of the spectrum with this particular apparatus, and with a normal exposure and development. So far, this teaches very little; it merely indicates that this particular plate is sensitive or insensitive to certain rays of colored light. To make this teaching of any value, we must institute comparisons. Accordingly, instead of simply exposing one plate, suppose we cut a strip from two, three, four, or even half a dozen different plates, and arrange them side by side, horizontally, in the dark slide, so that the spectrum falls upon the whole when they are placed in the camera and exposed. There is really no difficulty in cutting strips a quarter of an inch wide, the lengthway of a quarter plate. Lay the gelatine plate film up, and hold a straight edge on it firmly, so that when we use a suitable diamond we can plow through the film and cut a strip which will break off easily between the thumb and finger. A quarter plate can thus be cut up into strips to yield about a dozen comparative experiments. When cut and snapped off, mark each with pencil with such a distinguishing mark as shall be clearly seen after fixing. The cut up strips can be kept in the maker's plate box.

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The deep down underground electric railway in London has so far proved an unprofitable concern for its stockholders. It is 31/2 miles long, touches some of the greatest points of traffic, but somehow or other people won't patronize it. The total receipts for the last six months were a little under $100,000, and they only carried seventeen persons per train mile. On this road the passengers are carried on elevators up and down from the street level to the cars. The poor results so far make the stockholders sick of the project of extending the road.

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