82 



Mr. E. Scliimck on the Colouring and 



[EecesSj 



as well as the peculiar odour and taste of urine are due, and he called it 

 the resin of urine. The deposit formed in the boiling liquid contained 

 also a black pulverulent body, which he found to be insoluble in water and 

 alcohol, but soluble in alkalies, forming with the latter dark-brown solu- 

 tions, from which it was precipitated by acids in thick black flocks. When 

 dry, it had a shining appearance resembling that of broken asphalt. Proust 

 called this the peculiar black substance from urine ; and after some specu- 

 lations on its nature and origin, he says that probably at some future time 

 the relation, at present quite unknown, in which it stands to other bodies 

 will be discovered. On repeating Proust's experiments, Berzelius obtained 

 nearly the same results ; but he was of opinion that these substances are 

 not contained as such in the urine, as Proust had supposed, but are formed 

 by the action of acids on the extractive matters of urine. In this opinion 

 I entirely concur. Scharling's* oxide of omichmyle does not seem to me 

 to diifer in any of its properties from Proust's resin ; but as Scharling, 

 instead of evaporation, employed congelation as a means of concentrating 

 the urine, and then extracted his so-called oxide with ether, there seemis 

 some reason for supposing that his substance may have preexisted in the 

 urine. On examining the further details of his process, it will be found, 

 however, that he used boiling caustic lye for the purpose of purifying it ; 

 and it need hardly be observed that no conclusion can be drawn regarding 

 the preexistence of any organic compound which has passed throua-h a 

 process of purification involving the use of such an energetic agent as 

 caustic alkali. In the course of his experiments on the constitution of 

 urine, Liebigf also obtained the resinous substance of Proust, and he found 

 it to possess in general the properties previously ascribed to it. The 

 results of this portion of his investigation v/ere summed up in the follow- 

 ing words : — From the preceding it follows that human urine contains, as 

 organic acids, uric acid and hippuric acid, and another nitrogenous sub- 

 stance (most probably the colouring-matter of urine) which, in contact 

 with air (it is only in contact with air that, as already observed by Gay- 

 Lussac, the putrefaction of urine, accompanied by absorption of oxygen, 

 takes place), is decomposed, yielding acetic acid and a resin-like substance." 



In my paper on the occurrence of indigo-blue in urine, I gave a short 

 account of some experiments on these brown colouring-matters, and the 

 phenomena attending their formation. I there stated that " 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 dis- 

 solves, however, in a boiling mixture of alcohol and ammonia." These 

 facts were previously known from the researches of Proust. I succeeded, 



^ Annalen der Chem. und Pliarm., B. xlii. S. 265. 

 t Ibid. B. 1. S. 161. 



