CHAPTER XXXIX. UROXANTHINE, OR INDICAN. UROGLAUCINE, OR INDIGO BLUE. URRHODINE, OR INDIGO red. History. PERHAPS the earliest record of the occurrence in urine of a blue colouring matter is that by Janus Plancus.1 The first chemical description of a blue or violet colouring matter occurring in urine was given by Braconnot, who termed it cyanourine, and though he found that it had some similarity to indigo, believed it to be a separate organic base. There are several cases on record, where a substance corresponding in character to cyanourine was discovered in urine. The first reliable observation, however, of the occurrence of indigo in urine is by Prout. The same substance afterwards also occurred to other observers. Heller succeeded in extracting from urine a yellow substance, uroxanthine, which by treatment with acids at a higher temperature he could divide into a blue colouring substance, uroglaucine, and a red pigment, urrhodine. Cyanourine was proved by him to have been a mixture of these two bodies. Kletzinsky showed the identity of uroglaucine with indigo blue, and of urrhodine with indigo red. Virchow confirmed the observations of Heller, which had been ignored, doubted, or misrepresented' by many authors. 14 Commentarii Instituti Bononiensis,' ad. ann. 1767. 2 Ann. d. Chim. et de Phys.,' xxix, p. 252. 3 On Stomach and Urinary Diseases,' 3d edit., p. xcvi. Heller's Archiv,' 1845. 5 Ibid., vol. vi, p. 414. 6 Virchow's Archiv,' vol. vi, p. 259. 7 Heller's observations have been ignored by many authors. The latest among them is Neubauer, who, besides his own case of blue matter obtained from urine, takes no notice of hundreds of similar instances observed before him. Heller's observations have been doubted even by such chemists as Robin and He also found that, when much indigo-producing substance was present, the urine gave the copper-test for sugar. He also obtained uroglaucine from every concentrated urine. Latterly Schunck found indican, identical with Heller's uroxanthine, in urine, which indican he had before discovered to be the chromogen contained in indigoferous Verdeil. On this indifference Virchow justly remarks in his article quoted above; these authors might have avoided inflicting a great injustice upon Heller by their groundless objections, if they had chosen to satisfy themselves by the experiment. The same applies to Dr. G. Bird, who, in p. 331, expresses himself as follows: "Dr. Heller has lately stated that these curious deposits are merely metamorphosed uroxanthin or yellow colouring matter of urine, and has applied the name of uroglaucine to the blue pigment. He assumes, therefore, that it is identical with what I have described as purpurine, produced by the action of hydrochloric acid upon previously warmed urine. The statements of Heller, however, are mixed up with certain inaccuracies, and can hardly be admitted without more minute investigation." As Hassall, in p. 308 of his last paper in the Philosophical Transactions,' has similarly misrepresented Heller, I may here correct both errors at once. Heller never stated that uroxanthine was the ordinary, normal, or yellow colouring matter of urine. To that, he applied the name of urophæine. From 1845 to 1857, Heller has always asserted that there is scarcely a trace of uroxanthine in healthy urine, and that its occurrence in urine in any appreciable quantity was strictly pathological. Heller never assumed uroglaucine to be identical with Dr. G. Bird's purpurine; to this substance he applied the name of uroërythrine, and described its properties with the most minute details. He also maintained that uroerythrine was destroyed during the evaporation of urine, while Dr. G. Bird obtained his purpurine, not only from the deposits of urates, but also by extracting with alcohol the residue of the evaporation of urine. Urerythrine and purpurine are consequently only identical, so far as they occur as the colouring principles of deposits of urates. The production of purpurine by the influence of hydrochloric acid upon the normal colouring matter of urine, is Dr. Bird's exclusive property. The names of urophæine and urerythrine, Heller has adopted from Simon. Heller is therefore, in p. 115 of Dr. Bird's work, misrepresented as having applied the name of urrhodine to what Simon had called urerythrine, after Dr. Bird had given it the name of purpurine. Urrhodine may turn out to be identical with purpurine and urerythrine, but Heller kept them distinct. Urerythrine he found ready in the urine; urrhodine he produced from a substance, which he was the first to discover, uroxanthine. The crystals of uroglaucine described by Heller, and stated by Dr. G. Bird (p. 114) and Messrs. Robin and Verdeil, to be uric acid merely tinted by changed colouring matter, are really crystals of indigo, as Virchow also confirms, and as the most trivial experiment can confirm. Uric acid crystals could never be obtained in the manner in which Heller obtained his crystals of uroglaucine. At p. 115 of the edition of Dr. G. Bird's work by Dr. Birkett, there is, indeed, a foot-note, in which uroxanthine, uroglaucine, and urrhodine are mentioned in succession, and in which it is stated that the experiments regarding uroxanthine and urrhodine were so incomplete as not to admit of any conclusion. Three years ago these experiments were so complete, that the latest discoveries of Dr. Schunck have fully borne them out. It is surprising that on the same page the clearest proved facts should be doubted, where such coin as "sulphur extractive" is taken for good cash. I hope that my remarks will contribute to put a stop to so general a confusion, in which even Virchow participated, by believing the purpurine of Dr. Bird and rosacic acid of Proust (not Prout) to be identical with cyanourine and uroglaucine. Phil. Mag.,' S. 4, vol. xiv, No. 93, Oct., 1857, p. 288. plants, and which, under the influence of acids or ferments, yields indigo blue, a peculiar kind of sugar, and a small quantity of other products. Schunck found indican in almost every urine; and his observations strongly support the opinion that indican is a normal ingredient of human urine and the urine of many animals. UROXANTHINE, OR INDICAN. The chromogen of indigoferous plants is a peculiar colourless substance, which has been obtained (from Isatis tinctoria for example) by extraction with alcohol, precipitation of the extract by acetate of lead, and decomposition of the precipitate, first by carbonic acid, afterwards by hydrothion, when it remained in solution in the filtrate. On evaporation there remains a gum-like mass, indican, which, when boiled with acids, yields indigo blue, a peculiar description of sugar, and a small quantity of other matters. This indican had long been discovered and described by Heller, who did, however, not observe that sugar was one of the products of its decomposition by acids; but, having discovered the generation of indigo blue and indigo red under the influence of these agents, he shared the error, then almost general, of uroxanthine and the chromogen of the indigoferous plants being white or reduced indigo. Heller precipitated urine by acetate of lead, and evaporated the filtrate to dryness at a low temperature. He then extracted it with ether, which after evaporation left uroxanthine. Schunck, having ascertained the peculiar nature of indican, proceeded to obtain evidence of its presence in urine, in the following manner: When muriatic or sulphuric acid is added to urine, the mixture on being heated becomes brown, and begins to deposit dark-brown flocks, which increase in quantity when the heating is continued. When these flocks are filtered off, washed, and dried, they form a compact, dark-brown mass, from which cold alcohol extracts a resinous matter, leaving undissolved a brown powder, which dissolves, however, in a boiling mixture of alcohol and ammonia. This powder resembles, but is not, indifuscine, one of the products of the decomposition of indican. If the liquid filtered from these flocks be mixed with a salt of oxyde of copper and an excess of caustic soda, it becomes greenish, and if after being filtered it be heated for some time, it gradually deposits a tolerably large quantity of suboxyde of copper, which is a proof of the presence of sugar. That the latter has been formed during the process, and did not pre-exist, may be ascertained by previously heating a portion of the urine with a salt of copper and caustic soda, before treating the remainder of it with acid. Samples of urine, which, when tried in this way, afforded very doubtful or no indications of their containing sugar, were found, after being boiled with acid, then filtered and made alkaline, to reduce oxyde of copper in a very marked manner. This reaction proves, that there is contained in urine some body, which by decomposition with acids yields sugar, the brown flocks precipitated at the same time being probably the substance with which the sugar was originally associated in the form of a copulated compound. Schunck found that the composition of these flocks was expressed by the formula C14H,NO, which is also that of anthranilic acid, a product of the decomposition of indigo blue. Indican, or uroxanthine, is soluble in water, alcohol, and ether. By decomposition, under the influence not only of boiling acids, but also of ferments, it yields indigo blue, indigo red, and sugar, as the principal products. Occurrence of Indican. According to Heller, uroxanthine is present in the largest proportion in those specimens of urine from patients, which on addition of hydrochloric acid assume a blue tint. Such urine occurs most frequently in diseases of the serous membranes, the kidneys, and the spinal marrow. Schunck has demonstrated the existence of indican in almost every specimen of healthy urine, and thus confirms Virchow, who had already found that indigo blue might be obtained by Heller's process from almost every concentrated urine. Products of the Decomposition of Indican.-Indigo Blue and Indigo Red. in both substances Elements: CH, NO2, identical in (Schunck). Mode of obtaining these substances pure. a. From the indigo of commerce. -When the indigo of commerce is boiled with dilute acetic acid, indigo glue goes into solution, and may be obtained from it by evaporation, as a yellowish, varnish-like mass, which is soluble in water and alcohol. The substance thus freed of indigo glue is next treated with solution of caustic potash, which dissolves indigo brown. This latter substance may be precipitated from the solution in potassa, by the addition of sulphuric acid, in the shape of a voluminous brown mass, which possesses an acid reaction. Indigo thus treated with acid and alkali yields to boiling alcohol a red colouring matter, indigo red (indirubine of Schunck), which on evaporation of the alcohol remains in the form of a reddish-brown powder, soluble, with a dark-red colour, in alcohol and ether. On heat being applied to it, it is partly sublimated without decomposition; another part is decomposed, and yields a sublimate of colourless crystals. After the extraction of indigo red there remains indigo blue, which constitutes the greater bulk of the substance originally employed. This indigo blue may be further purified in the following manner. Crystalline indigo blue by sublimation.-Roughly powdered indigo is placed in a shallow china dish, and heated cautiously. On the surface of the fragments there are formed reticular masses of crystals, consisting of pure indigo blue. When heated in a glass tube, indigo evolves purple fumes, which suddenly condense, and settle on the surface of the powder from which they were evolved. It is, however, impossible to conduct the sublimation, so as not to destroy a part of the indigo by overheating. For the production of larger quantities of pure indigo blue, the following process is therefore more profitable. Crystalline indigo blue by reduction.-On mixing powdered indigo with grape-sugar, spirits of wine, and concentrated solution of caustic soda, and immediately closing the bottle and letting stand for some time, a yellow solution of indigo white, or reduced indigo, in the alkali, results, by the grapesugar withdrawing one equivalent of oxygen from the indigo blue. If the clear fluid is now decanted, and exposed to the air, the reduced indigo takes up again the lost equivalent of oxygen, and becomes indigo blue, which is slowly deposited in a crystalline form. Amorphous indigo blue by reduction.-If common indigo is mixed with caustic lime and a solution of sulphate of suboxyde of iron, and, the air being excluded at the same time, is allowed to stand for some time, the suboxyde of iron by withdrawing oxygen transforms indigo blue into indigo white, which latter is soluble in lime. When the clear yellow solution is poured into dilute hydrochloric acid, and |