26 Investigations on the Specific Heat of Solid and Liquid Bodies. {1, . have given to chemical analysis valuable processes for the separation of certain bodies. Toxicology and physiological chemistry especially will profit largely from methods of dialysis. For some months I have followed up these researches in the medical laboratory of the College of France, and beg permission to submit to the Academy my preliminary results. Graham has shown that by the aid of dialysis very minute quantities of certain poisons, mixed with various organic matters, may be detected, especially arsenious acid and strychnine; and I have myself already experimented on morphine, brucine, and digitaline. 1. Dialysis of Digitaline.—Place in the dialyser 100 cubic centimetres of distilled water holding in solution o gr. or of pure digitaline. Suspend the dialysis after twenty-four hours; carefully evaporate to dryness the liquid contained in the outer vase in a weighed platinum capsule. It will leave a residue weighing exactly o gr. o1, with a bitter taste, and presenting the characteristics of digitaline, of which more further on. July 1864. In the course of this preliminary study I endeavoured to find some reaction as much as possible characteristic of digitaline. Hitherto we know no reaction for distinguishing digitaline from other vegetable poisons, except the green colour obtained by dissolving this substance in concentrated hydrochloric acid. This reaction, as has been observed, cannot be taken as an unfailing indication of the presence of digitaline, for the same colour is produced by several other organic matters. The successive action of sulphuric acid and bromine vapours have hitherto seemed to characterise even very small quantities of digitaline. Pure digitaline takes a siennabrown colour on contact with concentrated acid, turning after a time to vinous red, and on the addition of water immediately becoming dirty green. When, instead of operating on, for instance, i centigramme of solid digitaline which has not yet been in contact with any liquid, we submit to the action of sulphuric acid the residue of the evaporation of several drops of a diluted solution of digitaline, the colour, instead of brown, is lighter or darker reddish-brown, according to the quantity of material employed. With very small quantities of digitaline (o gr. 0005, for instance), the colour is rose, like the flower of the digitalis. On exposing digitaline, moistened with sulphuric acid, to bromine vapours, the 2. Dialysis of Urine, containing 1 gr. 01 of mixture instantly becomes violet, and the shade varies Digitaline.—Into 45 cubic centimetres of fresh normal from heartsease violet to mauve, according as there is urine pour 2 cubic centimetres of a solution containing present more or less digitaline. The coloration shown o gr. 50 of digitaline to 100 centimetres cube of water; by sulphuric acid, and modified by bromine vapours, is after eighteen hours suspend the dialysis and evaporate most distinct with the residue of the evaporation of to dryness the liquid in the outer vessel (about 300 1 centimetre cube of water containing o gr. 005 of digicubic centimetres). Extract the almost colourless residue taline; it is also very clear with o gr. 0005 of this by alcohol; and the alcoholic solution, evaporated to dry- poisonous substance. It is observable with even the ness, shows all the characteristics of digitaline with as very faintest traces of digitaline. None of the followmuch clearness as the residue of two cubic centimetres of ing substances, which I have submitted to the same the normal solution of digitaline. Evaporate separately reaction, has evidenced this property::- Morphine, the contents of the dialyser, and the residue will be narcotine, codeine, narceine, strychnine, brucine, atrobrown; then extract by alcohol of 95°, and the pine, solanine, salicine, santonine, veratine, phlorhidzine, greenish solution thus obtained will give all the reactions daturine, amygdaline, asparagine, cantharidine, cafeine. indicating the presence of traces of digitaline. The dialysis then was not complete. Evaporate to dryness in a weighed platinum vessel the liquid remaining in the dialyser; it volatilises, leaving no residue, all the digitaline having passed into the dialysed liquid. 3. Dialysis of Morphine, Brucine, and Digitaline Mixed with Animal Matters. Take the stomach and intestines of a dog (some hours after death), macerate them in water at 25° or 30° for about two hours; filter the yellowish, strongly-smelling liquid through canvas. Divide it into four parts, each of 250 cubic centimetres; to the first add o gr. 04 of digitaline; to the second, o gr. oz of brucine; to the third, o gr. oz of hydrochlorate of morphine; leave the fourth intact; dialyse these four liquids separately. After twentyfour hours carefully evaporate the liquids contained in the outer vessels; recover each of the residues by alcohol, to separate the mineral salts (salts of soda, lime, &c.) which have been dialysed. The ordinary reagents of brucine (nitric acid) and of morphine (nitric acid, perchloride of iron) clearly show the presence of these alkaloids in the residues of the alcoholic liquids. Digitaline is found equally in the water of the first vessel. Divide the residue of the evaporation of that portion of the liquid to which no vegetable alkali was added into several parts, and test it with the reagents used to discover brucine, morphine, and digitaline. This experiment is merely intended to show that the animal matters, to which the poisonous substances are added, do not by themselves give, with reagents, colorations which might lead to error. The result of this test leaves no doubt as to the value of dialysis applied to researches of this kind. Dialysis and in this consists its greatest valueallows the separation of the vegetable poisons from the animal substances with which they are mixed, in a state sufficiently pure to enable us to identify them by their principal characteristics.-Comptes Rendus, lviii, 1048. PHYSICAL SCIENCE. Investigations on the Specific Heat of Solid and Liquid (Continued from Vol. IX., page 295.) THE author next discusses whether it is to be assumed that the elements enter into compounds with the atomic heats which they have in the free state. This assumption is cnly admissible provided it can be proved that the atomic heat of a compound depends simply on its empirical formula, and not on the chemical character or rational constitution. Much of what has previously been said favours this view of the case. It is also supported by the fact that similar chemical character in analogous compounds, and even isomorphism, do not pre-suppose equality in the atomic heats, if in one compound an atomic group (a compound radical) stands in the place of an elementary atom of another; for instance, the atomic heat of cyanogen compounds is considerably greater than those of the corresponding chlorine compounds, and those of ammonium materially greater than those of the corresponding potassium compounds. A further support for that assumption is found in the fact that, regardless of the chemical character, the atomic CHEMICAL NEWS, July 16, 1864. Investigations on the Specific Heat of Solid and Liquid Bodies. "} 299 The opinion that the elements enter into compounds with the atomic heats they have in the free state has been already expressed; but the view has also been defended that the atomic heat of an element may differ in a compound from what it is in the free state, and may be different in different compounds. The author comes to the result that the latter view is not proved and is in admissible. As the result of all these comparisons and observations, the author arrives at the conclusion:-Each element, in 27 the atomic heats of compounds are frequently not known with certainty, as is seen by the circumstance that analogous compounds, for which there is every reason to expect equal atomic heat, are found experimentally to exhibit considerable differences; but, secondly, because in such deductions the entire relative uncertainty in the atomic heats for a compound, and for that to be subtracted from its composition, is thrown upon a small number, the residue remaining in the deduction. The details of the considerations cannot be gone into by which the author deduces the atomic heat of the individual elements; the results simply, which are not all attained with equal certainty, may be adduced. The author adopts the atomic heat 18 for E, 23 for H, 2'7 for B, 37 for Si, 4 for →, 5 for Fl, 5'4 for P and £, 6·4 for the other elements for which or for whose compounds the atomic heat is known in somewhat more trustworthy manner, it being left undecided in the case of the latter elements, whether (in accordance with Dulong and Petit's law) they have the same atomic heats, or whether the differences in the atomic heats cannot at present be shown with certainty. heat has been investigated in a trustworthy manner, a The author gives for all compounds, whose specific comparison of the specific heats found experimentally with those calculated on the above assumption. The atomic heat of a compound is obtained by adding the atomic heats of the elements in it, and the specific heat by dividing this atomic heat by the atomic weight. The calculated specific heat of chloride of potassium, KCl, is are differences between calculation and observation met with which exceed these limits, or exceed the deviation between the results of different observers for the same substance. whole, a sufficient agreement between the calculated and A table, embracing 200 compounds, shows, on the the observed specific heats. The author remarks that a closer agreement between calculation and observation heats of such compounds, for which, from all we know cannot be hoped than that between the observed atomic the solid state and at an adequate distance from its melt-conformity with Neumann's law, to which, in such cases, at present, the same atomic heat is to be expected in ing-point, has one specific or atomic heat, which may of course, calculation corresponds. In only a few cases indeed somewhat vary with physical conditions, different temperature, or different density, for example, but not so much as to necessitate that being taken into account in considering the relation in which the specific or the atomic heat stands to the atomic weight or composition. For each element it is to be assumed that it has essentially the same specific heat or atomic heat in the free state and in compounds. He then passes on to determine what atomic heats are to be assigned to the individual elements. As data for determining this he takes (1) the atomic heats which follow from determinations of the specific heat of the elements in the free, solid state; (2) the atomic heats obtained for an element, if, from the atomic heat of one of its compounds, which contains beside it only elements of known atomic heat, the atomic heats corresponding to the latter elements are subtracted; (3) the difference found between the atomic heats of analogous compounds of an element of unknown, and of an element of known atomic heat, in which case the difference is taken as being the difference between the atomic heats of these two elements. The author dwells upon the fact that in the indirect deduction of an element by (2) and (3) the result may be uncertain: first, because If calculation of the specific heat does not supersede the necessity of experimental determination in the solid state, and does not give a trustworthy measure for the accuracy of such determinations, it gives a rough control for the experimental determinations, and it indicates would not have been noticed. sources of error in the experiments, which, without it, An instance may be adduced. The author found for sesquichloride of carbon Cle, which, according to Faraday, melts at 160°, the specific heat, between 200 and 50°, to be 0.276 in one number o°27 might from this be taken to express the series of experiments, and o°265 in another. Hence the But calculation gives specific heat of the compound. (2 x 18)+(6 × 6°4) 237 = o'177, a very different number. A third series of experiments, with substance once more recrystallised, gave for the specific heat between 21° and 49° 0'278, confirming the previous determinations. It 28 Application of Potassio-Ammonium Chromate to Photography. {CHEMICAL NEWS, might here appear doubtful whether calculation was not refuted by experiment. The discrepancy was removed by the observation that the substance is distinctly more viscous at 50° than it is at lower temperatures, and by the suspicion that it might at 50°, that is, 100° below its melting-point, already absorb some of its latent heat of vitreous fusion. This was found to be the case; two concordant series of experiments gave as the mean of the specific heat the numbers : Between 18° and 37° Between 18 and 50°. • 0*178 O'194 O'277 The first two numbers differ so little that it may be supposed the number found for temperatures below 37° is very near the true specific heat of this compound; it also agrees well with the calculated number. In the sixth part of his paper the author enters into considerations on the nature of the chemical elements. He calls to mind the discrepancy which has prevailed, and still prevails, in reference to certain bodies, between their actual indecomposibility and the considerations, based on analogy, according to which they were held to be compound. Even after Davy had long proclaimed the elementary nature of chlorine it was maintained that it contained oxygen. In regard both to that substance and to bromine and iodine, the view that they are peroxides of unknown elements still finds defenders. That iodine, by a direct determination of specific heat, and chlorine, by indirect deduction, are found to have an atomic heat in accordance with Dulong and Petit's law puts out of doubt that iodine and chlorine, if compound at all, are not more so than the other elements to which this law is considered to apply. According to Dulong and Petit's law, compounds of analogous atomic composition have approximately equal atomic heats. In general, compounds whose atom consists of a larger number of undecomposable atoms, or is of more complex constitution, have greater atomic heat, Especially in those compounds all of whose elements follow Dulong and Petit's law is the magnitude of the atomic heat a measure of the complication or of the degree of complication. If Dulong and Petit's law were universally valid, it might be concluded with great certainty that the so-called elements, if they are really compounds of unknown simpler substances, are compounds of the same order. It would be a remarkable result if the art of chemical decomposition had everywhere reached its limits at such bodies, which, if at all compound, have the same degree of composition. Let us imagine the simplest bodies, perhaps as yet unknown to us, the true chemical elements, to form a horizontal layer, and above them to be arranged the more simple and then the more complicated compounds; the general validity of Dulong and Petit's law would include the proof that all the elements at present assumed to be such by chemists lay in the same layer, and that in admitting hydrogen, oxygen, sulphur, chlorine, and the various metals as elements, chemistry has penetrated to the same depth in that range of inquiry, and has found at the same depth the limit to its advance. July 16, 1864. may have the same atomic heat as an element. Chlorine might certainly be the peroxide of an unknown element which had the atomic heat of hydrogen. The atomic heat of peroxide of hydrogen, He, in the solid state or in solid compounds, must be = 2.3 + 463, agreeing very nearly with the atomic heats of iodine, chlorine, and the elements which follow Dulong and Petit's law. In a very great number of compounds the atomic heat gives more or less accurately a measure for the complication of the composition. And this is also the case with those compounds which, from their chemical deportment, are comparable to the undecomposed bodies. If ammonium or cyanogen had not been decomposed, or could not be by the chemical means at present available, the greater atomic heats of the compounds of these bodies, as compared with analogous potassium or chlorine compounds, and the greater atomic heats of ammonium and cyanogen obtained by indirect determination, as compared with those of potassium and chlorine, would indicate the compound nature of those so-called compound radicals. The conclusion appears legitimate, that for the so-called elements the directly or indirectly determined atomic heats are a measure for the complication of their composition. Carbon and hydrogen, for example, if not themselves actually simple bodies, are yet simpler compounds of unknown elements than silicium or oxygen, and still more complex are the elements which may be considered as following Dulong and Petit's law. It may appear surprising, and even improbable, that so-called elements, which can replace each other in compounds, as, for instance, hydrogen and the metals, or which enter into isomorphous compounds as corresponding elements, like silicium and tin, should possess unequal atomic heats and unequal complication of composition. But this really is not more surprising than that undecomposable bodies and obviously compound bodies, hydrogen and hyponitric acid, or potassium and ammonium, should, without altering the chemical character of the compound, replace one another, or even be present in isomorphous compounds as corresponding constituents. The author concludes his memoir with the following words:"I have here expressed opinions in reference to the nature of the so-called elements, which appear to depend upon allowable conclusions from well-demonstrated principles. It is of the nature of the case that with these opinions the certain basis of the actual and of what can be empirically proved is left. It must also not be forgotten that these conclusions only give some sort of clue as to which of the present undecomposible bodies are of more complicated and which of simpler composition, and nothing as to what the simpler substances are which are contained in the more complicated. Consideration of the atomic heats may declare something as to the structure of a compound atom, but can give no information as to the qualitative nature of the simpler substances used in the construction of the compound atoms. But even if these conclusions are not free from uncertainty and imperfection, they appear to me worthy of attention in a subject which is still so shrouded in darkness as the nature of the undecomposed bodies.'" PHOTOGRAPHY. But with the proof that this law is not universally true, the conclusion to which this result leads loses its authority. If we start from the elements at present assumed in chemistry, we must admit rather that the magnitude of the atomic heat of a body does not depend On the Application of Potassio-Ammonium Chromate to on the number of elementary atoms contained in a molecule or in the complication of its composition, but on the atomic heat of the elementary atoms which enter into its composition. It is possible that a decomposable body Photography, by E. KOPP. (Continued from Vol. IX., page 296.) ALL the chromic acid is dissolved, and only oxide of chromium remains as residue by prolonged washing CHEMICAL NEWS Application of Potassio-Ammonium Chromate to Photography. July 16, 1864. simply in water, either pure, alkaline, or even simply calcareous. For this reason the washing of photographs should not be carried too far. Otherwise the brown image will become paler and paler; until it retains only the lightgreenish tint of hydrate of oxide of chromium. This ready alteration of the compound CrO, becomes in this respect a disadvantage, while in other respects it is equally an advantage. It allows the employment of operations of a very different nature to strengthen the image, and fix it permanently and unalterably. In fact, with the superoxide there are instantaneously fixed on the paper both chromic acid and oxide of chromium, and each of these two compounds, possessing a colouring power much more intense than that of CrO2, is capable of entering into new combinations. 1. If it is desired to fix chromic acid we have but to submit the paper with the image, previously washed, to the action of solutions of metallic salts capable of forming insoluble chromates (even in a slightly acid liquid) and highly coloured; such are the chromates of lead, bismuth, silver, mercury, &c. Thus, to cite but one instance, by shaking the photographs in a very weak but bright and limpid solution of mercurous nitrate, as neutral as possible, the image almost immediately assumes a decided orange-brownish red tint, produced by the formation of mercurous chro mate. With a salt of lead or bismuth the image would be yellow; with a salt of silver, crimson, &c. But the transformation is not thus limited; the image once fixed in the state of insoluble metallic chromate, it may be washed perfectly, in order to remove all trace of soluble metallic salt from the white parts, and nothing then prevents its undergoing the action of sulphuretted hydrogen, or alkaline sulphides, and the yellow, orange, or reddish-brown tints turned to more or less deep black. By this manner of operating it is evident that chromic superoxide furnishes the means of fixing on the paper, in quantities proportional to the intensity of the shades, various metallic salts which, once fixed, may be made apparent by various reactions if, in the state of chromate, the image is not of the desired tint. As reactions accompanied by phenomena of colour are extremely numerous and varied with the proper metals, which are precisely those which become fixed under the above circumstances, it is not unreasonable to suppose that among them some may be practically utilised. To give but one instance, by plunging the image formed by mercurous chromate into a weak solution of hyposulphite of soda the orange-brown will be observed to turn to black immediately, more or less brownish or greyish, consequent on the formation of black sulphide of mercury. 2. Setting aside chromic acid, new effects may be obtained by operating on the chromic oxide resulting from the alteration of CrO2. We have already observed that by leaving the image formed by CrO2 for a long time in water, especially in calcareous water, all the chromic acid gradually dis appears, and only hydrate of oxide of chromium remains on the paper. This result is obtained much more rapidly by washing with a diluted and warm solution of carbonate of soda, ammonia, or any other salt with an alkaline reaction, always finishing by washing in pure water. But the hydrate of oxide of chromium serves as a mordant, and it follows that on plunging the paper thus 29 modified into a bath containing a colouring matter susceptible of fixation by the mordant of chromium that an image will turn from its original pale green to the tints produced by this mordant. The colouring matters serving for this purpose being very numerous, such as alizarine, purpurine, Brazil, logwood, fustic, &c., &c., very varied effects can, of course, be produced, Logwood is especially fit for this purpose. It is by no means necessary that CrO, should be entirely transformed into Cr2O3; it suffices to wash it until no undecomposed chromate remains on or in the fibre of the paper. The small quantity of chromic acid remaining combined with the oxide of chromium operates favourably in modifying the tint of the logwood to bluish black. Also, after a certain period of immersion in a bath of logwood recently prepared, and hot, the image becomes very dark bluish black. The white parts even become much coloured after a time, but they are easily restored. After the dyed paper has been washed, it is plunged into a very weak and tepid solution of chloride of lime, where the undyed parts become rapidly white, and the image reappears. The reaction is brought to an end when the desired tint appears; the paper is then washed and dried. With other colouring matters the operation is conducted in much the same manner, subject to modification according to circumstances and the peculiar nature of the dye. Paper, however close and strong it may be, is, for this kind of preparation, very inconvenient. In prolonged washing in water, especially in hot water, the fibres are raised, and the image loses some of its distinctness; besides, the paper almost always contains some mineral matters, such as alum, chalk, &c., possessing an affinity, more or less marked, for the colouring matter. These defects are inherent to the nature of ordinary paper, and, to obviate them, it would perhaps be better to use a paper specially prepared; for instance, parchment paper, so that the fibres could not be easily separated, and that they might be free from matters capable of taking the place of mordants. There is evidently no reason why a more or less fine cloth should not be substitnted for paper and operated upon in the same manner. The reactions we have described may be regarded as constituting one of the phases of the application of photography to the production of designs on tissues. Many manipulations difficult, if not impossible, on paper, are perfectly easy of cotton, woollen, or silk materials. 3. The compound Cro, fixed on paper and cloth has yet another series of reactions, several of which may be utilised. 2 They are founded on the property possessed by Cro, of acting as a superoxide readily abandoning its oxygen, becoming an oxide, and consequently exercising a strongly oxidising action. By putting in contact with CrO, a body which, while oxidising, forms an insoluble compound, this compound will become fixed at every point where it encounters chromic superoxide. Among organic compounds there are several which answer this purpose, and which besides assume more or less dark tints, such, for instance, as certain pyrogenic acid, astringent substances, several naphtha and anilic combinations, &c. They are equally to be found among minerals, and to give but one example we will mention that by plunging a paper coloured by CrO, in a weak, cold, and perfectly neutral solution of a ferrous salt (sulphate or chloride) it will after a time be found that oxide of iron is pre- PROCEEDINGS OF SOCIETIES. CANTOR LECTURES. {CHEMICAL NEWS, July 16, 1864. Gelatine of best glue in one pound of water, and adding gradually "On Chemistry Applied to the Arts." By Dr. F. CRACE with hydro-sulphate of ammonia, so as to produce an imi CALVERT, F.R.S., F.C.S. GELATINE, GLUE, BONE-SIZE, CHONDRINE, their preparation, chemical properties, nutritive value, and application to arts and manufactures. Artificial tortoiseshell. Isinglass, its adulterations and adaptations to the clarification of fluids. Skins and the art of tanning. LECTURE II. DELIVERED ON THURSDAY EVENING, APRIL 7, 1864. As the syllabus will show you, I intend to draw your attention, especially in this lecture, to gelatinous substances, as well as to the art of tanning. There are four distinct gelatinous substances obtained on a commercial scale from animal tissues and bones, viz.,-Osséine, which I mentioned in my last lecture, Gelatine, Chondrine, and Isinglass. Osséine, as already stated, is the animal matter existing in bones, and no doubt it is the same substance which also exists in skins, both during life and when recently removed from the animal. It is characterised by its insolubility, its inability to combine with tannin, and lastly, the facility with which it undergoes a molecular change, and becomes converted into gelatine, slowly, when boiled with water at 212°, rapidly, when boiled under pressure at a higher temperature, and very gradually under the influence of putrefaction. Gelatine is a solid semi-transparent substance, which absorbs water in large quantities (40 per cent.), becoming thereby transparent. It is very slightly soluble in cold water, but very soluble in boiling water; and this solution has the characteristic property of forming a jelly on cooling. So powerful is gelatine in solidifying water, that one part of gelatine will form a jelly with 100 parts of water. It has been observed that gelatine loses this valuable property if boiled for a long time at ordinary pressure, or if carried to a temperature above 223° F. Before examining the interesting action of acids upon gelatine, allow me to mention that whilst solid gelatine resists putrefaction for a long time, its solutions have a tendency to putrefy rapidly, but I have the pleasure to inform you that a few drops of a substance called carbolic acid will prevent putrefaction for a long period. Gelatine dissolves rapidly in acetic acid, of moderate strength, or vinegar, and this solution, which is used as glue, has the useful property of remaining fluid and sound for some time. But a Frenchman, named Demoulin, has introduced of late years in Paris a solution of glue which is superior to the above and to that in common use, because it does away with the trouble of constantly heating the glue-pot. His process consists in melting one pound tation of the grain of tortoiseshell. The objects so produced are then polished and ready for sale. Before entering on the manufacture of various qualities of gelatine, I should wish to state that there can be no doubt, from the researches of Magendie, as well as from the Report of the Commission appointed by the Netherlands Academy of Sciences, that gelatine as food possesses no nutritive value whatever. Allow me now to give you a rapid outline of the methods followed in the manufacture of various qualities of gelatine. The first quality of gelatine is prepared by taking the clippings, scrapings, and fleshings from the tanyard, treating them with lime water or alkali, to remove any smell and certain impurities. They are then well washed and left in contact for a day or two with a solution of sulphurous acid. They are then placed in a suitable apparatus with water, and heated, when the osséine is converted into gelatine. This is run into a second vessel, and a little alum added, to throw down any impurities that may be in suspension. The liquor is now ready to be run into another pan, where it is concentrated to the necessary consistency, so as to become solid when it is run into wooden moulds. Eighteen hours afterwards the gelatine is turned out of these moulds on to a wet slab, where it is cut into slices by means of a copper wire; these slices are placed on wire gauze frames, and left in a drying shed until they are perfectly dry and ready for the requirements of trade. The second quality of gelatine is prepared by placing bones in large cylinders, and allowing high-pressure steam to arrive at the bottom of the cylinder, which rapidly converts the osséine of the bones into gelatine, and the removal of this is facilitated by allowing a stream of hot water to enter the upper part of the cylinder. The solution of gelatine thus obtained is evaporated, and is usually employed for the preparation of glue. A third quality is prepared by treating bones with hydrochloric acid (as referred to in my first lecture), and submitting the osséine thus obtained to the action of steam. Lastly, a fourth quality of gelatine, called bone-size, is manufactured by boiling more or less decayed bones, as imported from South America and elsewhere, the flesh of dead animals, &c., and concentrating the solution to the consistency required for the various applications it receives in commerce. [The lecturer then described the mode of obtaining the beautiful thin coloured sheets of gelatine used in photography and other fancy purposes, and also the characteristics which distinguished good from bad glues.] Chondrine, or cartilage gelatine, first noticed by Messrs. |