78 



Mr. E. Scluuick on the Colouring and 



[Eecess^ 



The solution in ammonia gave copious broY/n precipitates, with metallic 

 salts. Marcet concludes from the experiments of Prout that this so-called 

 acid hears a close analogy to the products derived from uric acid; but 

 Berzelius remarks that it strongly resembles the black pulverulent substance, 

 insoluble in alcohol, which is formed by the action of concentrated acids 

 on the extractive matters of urine. By heating the urine yielding cyano- 

 urine, after separation of the latter by filtration, Braconnot obtained a 

 black sediment which he called melanourine. I should at once have assumed 

 that this substance was identical with Front's melanic acid, if Braconnot 

 had not stated that his black pigment was soluble in weak acids and in- 

 soluble in alkalies, whilst the behaviour of melanic acid to acids and 

 alkalies is exactly the reverse. Considering the facility with which the 

 ordinary extractive matters of urine are decomposed, jdelding products in- 

 soluble in water of a black or brown colour, it is surprising that urines 

 containing these bodies ready formed should not more frequently be met 

 with in cases of disease. It is not improbable, hovrever, that the dark- 

 brown colour of some urinary calculi may be owing to one or the other of 

 these bodies. 



II. The second class of urinary colouring-matters comprises those v/hich 

 are formed from urine by artificial means, and consequently do not exist 

 ready formed in the secretion. These may also be classified according to 

 colour, those which have hitherto been observed being either blue, red, or 

 brov/n. 



I believe that Heller* was the first to obtain artificially from urine 

 colouring-matters of a pure blue or red tint. He states, in his first mem.oir 

 on the subject, that in som.e diseases the urine contains a notable quantity 

 of a body of a light yellow colour, and easily soluble in water, which ho 

 calls uroxanthine. When urine containing this body is exposed to oxidi- 

 zing agencies, such as nitric acid, or even atmospheric air, it deposits a dark- 

 coloured sediment, consisting of a blue and a red colouring-matter, named 

 by him respectively iiroglaucine and urorhodine. The former, after being 

 purified, appears in small groups of crystals of a dark-blue colour, which 

 are insoluble in water, as well as in cold alcohol and ether, but soluble in 

 boiHng alcohol. Urorhodine, according to Heller, is formed by a lower de- 

 gree of oxidation than uroglaucine. It is easily soluble in cold alcohol or 

 ether, to which it communicates a splendid crimson colour, and is always 

 am.orphous and apparently of a resinous nature. Uroxanthine, the body 

 from which these colouring-matters are derived, and which, according to 

 Heller, is itself probably derived from urea, is also contained in small 

 quantities in normal urine. Braconnot's cyanourine is, in Heller's opinion, 

 a mixture of uroglaucine and urorhodine. In two subsequent memoirs f 

 Heller communicated some further details on the preparation of these 

 colouring-matters from urine, and on their occurrence in a urinary calculus, 

 without, however, adding any new facts to those previously known regard- 

 Heller's Arcliiv, 1845, S. 161. t Ibid. 1846, S. 19, 536. 



