Mode of obtaining Allantoine. The allantoic fluid of the cow (which is mostly mixed with amniotic liquor) is evaporated to one quarter of its original bulk, and cooled down to make allantoine crystallise. Allantoine is also precipitated from the fluid, when it is allowed to stand for some length of time, and may then be separated, dissolved in hot water, and, after filtration, recrystallized. The urine of calves is obtained (according to Wöhler) by tying the bladder before the animals are killed by the butcher. This proceeding can only be adopted in countries where the calves are killed very early, as in Germany and Switzerland. In this country, therefore, other proceedings must be had recourse to for obtaining the urine. Among those which are practicable, the catheterism of female animals appears to be most suitable. The urine thus obtained is evaporated on the water-bath to a syrupy consistence, and is put in a cold place for several days, then diluted with water. The gelatinous precipate of urate of magnesia is then removed by washing, when there remain only crystals of phosphate of magnesia and allantoine. They are now washed with a little cold water, boiled with water and a little good animal charcoal, and filtered, when most of the phosphate of magnesia remains on the filter. The addition of a few drops of hydrochloric acid to the filtrate keeps in solution the phosphate of magnesia, and, on cooling, colourless allantoine crystallizes from the solution (Wöhler). Städeler obtained allantoine from the urine of a dog as follows: The urine, immediately after passing, was precipitated with basic acetate of lead, and the excess of lead was removed from the filtrate by sulphuric acid and hydrothion. The colourless fluid was evaporated on the water-bath. The residue was extracted with boiling spirits of wine of 82 per cent., and the yellowish solution put aside in a well-closed bottle. After the lapse of several days a large quantity of small white groups of crystals appeared deposited upon the sides of the bottle, which were almost insoluble in cold water, but dissolved in boiling water, and on cooling were deposited again in larger glistening crystals. This body was allantoine. Mode of obtaining allantoine from uric acid.-Powdered uric acid is suspended in little water, and heated to near the boiling point. Peroxyde of lead in a finely powdered state is now added to the fluid, which is continued to be kept hot, until the last portions of the peroxyde are no longer transformed into a white mass. The mixture is now filtered hot, and the filtrate, on cooling, and on further evaporation and cooling, yields allantoine in crystals; the mother-liquor contains urea, from the last traces of which the crystals of allantoine may be separated by recrystallization. Physical and Chemical properties. Allantoine crystallizes in glass-like needles; when obtained from uric acid it represents rhomboedric crystals, combined with the hexagonal prism or column. It is tasteless, colourless, and has no reaction on test-paper. Exposed to the air it undergoes no change; it contains no water of crystallization. Subjected to dry distillation, it yields carbonate and hydrocyanate of ammonia, empyreumatic oil, and a spongy charcoal. Heated with oil of vitriol it is decomposed into sulphate of ammonia and a mixture of carbonic acid and oxyde of carbon. When gently warmed with nitric acid of a specific gravity of 12 to 14, during which process no gas is evolved, the solution on cooling yields nitrate of urea in crystals. The solution, on being evaporated to dryness, leaves nitrate of urea and allanturic acid. The same decomposition of allantoine can be brought about by boiling it with hydrochloric acid, by heating it enclosed with water in a strong tube to a temperature of from 110° to 140 C. (230° to 281° F.) (Here urea is further decomposed into ammonia and carbonic acid.) Allantoine is soluble in 160 parts of cold water, in 30 of boiling water; it is soluble in hot alcohol, and crystallizes from both these hot solutions on cooling. It is soluble in cold solution of caustic potash, and is precipitated from this solution by the addition of acids. If, however, allowed to remain in this solution for any length of time, it is metamorphosed. It is soluble in solutions of the carbonates of the alkalies. When boiled with hydrate of potash or baryta, it is resolved into ammonia and oxalic acid. The same decomposition takes place under the influence of yeast, at a temperature of 30° C. (86° F.) Urea, oxalate and carbonate of ammonia, and a new acid, not investigated, are the products of the decomposition. On adding to a boiling saturated solution of allantoine in water nitrate of silver, and then ammonia, so long as a precipitate is being formed, a combination of allantoine with oxyde of silver is obtained in the precipitate, which is a white glistening powder, and under the microscope appears in spherical balls. It is decomposed by all dilute acids, allantoine being set free. A solution of allantoine is not precipitated by corrosive sublimate. It is, however, precipitated by a solution of nitrate of protoxyde of mercury, and, like urea, combines with mercury in various proportions, analogous to the compounds of urea. (Limpricht.) It enters into combination with the oxydes of copper, cadmium, lead, and zinc, and the combinations crystallize. Pathological indications. In consequence of having found allantoine in the urine of a dog suffering from dyspnoea following the injection of oil into his veins, Frerichs and Städeler examined the urine of several persons suffering from dyspnoea, emphysema, and pneumonia, as also the urine of a woman who, to relieve the dangerous dyspnoea caused by an aneurism of the arch of the aorta, was obliged to have tracheotomy performed upon her. In neither of these cases were the observers able to find allantoine in the urine. It is therefore yet questionable how the appearance of allantoine in the urine of the dog has to be explained. It is also a question whether allantoine ever appears in the urine of man. But as there is a probability, I have thought it best not to omit the description of its properties, in order that there might be less chance of its being overlooked by future observers. In its elementary composition it stands near to guanine, only containing one equivalent of nitrogen and hydrogen less than that base. It also presents great analogies to it in its compounds. Its elementary composition is identical with that of hypoxanthine, the base discovered by Scherer in the spleen, and since found by him in various organs. The two substances likewise agree in certain other characters; hypoxanthine, however, is almost insoluble in water and hydrochloric acida difference from carnine, which cannot be accounted for by simple difference of purity of the preparations. Hypoxanthine dissolves in warm nitric acid with evolution of gas, and on cooling yields a product of decomposition. The solution in nitric acid, on evaporation to dryness, leaves a yellow residue, assuming a red colour on the addition of caustic potash. Carnine, on the other hand, dissolves in nitric acid without evolution of gas, and the solution by evaporation on the water-bath, leaves a colourless mass, which does not become yellow unless very strongly heated; on addition of potash this residue assumes a red colour. Xanthine and guanine have very similar reactions. 10 From its elementary composition, xanthine (CH,N ̧O1) might be considered as a compound of uric acid with carnine, 2C10H1NO1 = C10H ̧NO + C1H ̧Ñ ̧O2; 4 Xanthine. 10 4 6 101 41 Carnine. but its chemical affinities do not accord with this view. By mixing a solution of hydrochlorate of carnine with urate of soda, not xanthine, but an isomeric compound-urate of carnine is obtained, which, under the influence of acids, separates into its original constituents. Wollaston, Philos. Transact.,' 1810, p. 223.-Cystine discovered, constituting a calculus, 1810. Baudrimont and Malaguti, Journ. d. Pharm.,' vol. xxiv, p. 633.-Proved the presence of sulphur, which had been overlooked by Prout and Lassaigne. Thaulow, 'Ann. d. Pharm.,' vol. xxvii, p. 197.-Best elementary analysis. Marchand, Journ. d. Pract. Chem.,' vol. xvi, p. 255. For the rest of the casuistic see Gmelin's Handb. d. Org. Chem.,' 4th edit., vol. ii, p. 133. Occurrence. Cystine is the principal constituent of a rare description of calculus; small calculi are sometimes made up of pure cystine, and then appear yellow, transparent, wax-like, of a crystalline texture. They cut like dry walnut, may be powdered, and are gritty between the teeth, tasteless, and neutral. When the calculi are not made up of pure cystine, they generally contain an admixture of earthy phosphates, and then are greenish-blue, dirty greenish-grey, or fawn-brown. |