Colouring-matter of Human Urine. 



35 



In a slight depth the band at F had disappeared. The pigment was 

 also soluble in nitric acid and in lactic acid ; in the former there were 

 no bands, except that at F, visible ; in the latter they resembled those 

 of the acetic acid solution. 



All the spectra which I have described will suffice to show that the 

 same pigment was evidently present in every solution ; there were 

 many more observed and measured, but they were not of sufficient 

 importance to call for their being mentioned here. 



It now became necessary to test the urobilin prepared by the hydro- 

 chloric acid process for sulphur, which was accordingly done ; and not 

 only was sulphur found to be absent, but the presence of chlorine was 

 detected, showing that my inference was correct, and that the sulphur 

 found in the urobilin prepared by the sulphuric acid process was due 

 to the sulphuric acid used in its preparation, and that the chlorine 

 found in the urobilin prepared by the hydrochloric acid process was 

 due to the hydrochloric acid. But in neither case was there free sul- 

 phuric acid or free hydrochloric acid, and hence the conclusion follows 

 that the urobilin was in combination with those acids respectively. 



I think it will be allowed that the bands visible only at certain 

 depths of the solution belong to the same pigment that gives the band 

 at F, hence they all belong to urobilin. As they are not visible in the 

 aqueous solution, we can understand why they are not visible in urine. 

 And I may also mention that, although water only appears to take up 

 a pigment giving a band at F, yet after evaporation of the water and 

 solution of the residue in alcohol, ether, or chloroform, the same bands 

 again become visible. 



Summary. 



1. Urobilin has been separated from urine. 



2. It has been separated in combination with hydrochloric acid and 

 with sulphuric acid respectively. 



3. The spectra of solutions of urobilin obtained by these methods 

 respectively differ in the position of certain feeble bands, but agree in 

 all having a black band at F, which can be made to disappear on adding 

 ammonia in excess, and which is replaced by another band nearer the 

 red end of the spectrum on the addition of sodic hydrate. 



4. Urobilin is an amorphous brownish-red pigment, which contains 

 carbon, oxygen, hydrogen, and nitrogen. It is soluble in alcohol, 

 chloroform, acidulated water, acids ; partially in ether, benzol, and 

 water, i.e., if the pigment be separated in combination with hydro- 

 chloric or sulphuric acid. 



5. Urobilin appears capable of existing in different states of oxida- 

 tion. 



6. Urobilin is derived from one of the colouring matters of bile. 



