l'i; '/'/(. Yellow Colonrimj Matter of the Uiine. [Apr. 2( 



gi-eat bulk of the pigment ; but, since we are ignorant of the form i 

 which the pigment exists in such precipitates, i.e., whether it is i 

 actual chemical combination with the precipitant, this objectio 

 does not appear to be insuperable, especially as other pigment 

 which are certainly definite compounds, appear to behave in a simila 

 way. 



There can, 1 think, be little doubt that the same substance foi 

 the basis of the products obtained by Thudichum, Tichborne, Schunc 

 and myself, such differences as were observed being due to varyi 

 degrees of purity, and probably to changes produced in the pigm 

 by the various methods of extraction employed. 



The most important respects in which my product differed 

 the urochrome of Thudichum were its behaviour with ether and wh 

 heated with mineral acids. 



The fact that ether, when shaken with normal urine, does 

 acquire any yellow tint suggests, but does not prove, that, in 

 original condition, the yellow pigment is insoluble in ether, and at 

 stage of my process is the product soluble in that medium. Ui 

 chrome, on the other hand, is described by Thudichum as being moi 

 readily soluble in ether than in alcohol. Again, a portion of Schunck 

 product (urian) was also soluble in ether. 



I have myself found that the pigment obtained from urine t 

 saturation with baryta, precipitation with the acetates of lead, an 

 extraction of the precipitate with cold dilute sulphuric acid, followc 

 by immediate neutralisation with ammonia, is to some extent solub 

 both in ether and in chloroform, and can only attribute this different 

 to a change produced by the process of extraction employed. 



When acted upon by hydrochloric or sulphuric acid upon a wai 

 bath, my product behaved more like those of Schunck than li 

 urochrome. The chief difference from Thudichum's results was t 

 no portion of the residue was soluble in ether with a red colon 

 I should, however, mention that I have repeatedly obtained a 

 stance yielding a rich red ethereal solution, when the speci 

 treated had not been freed from indoxyl sulphate, but never w 

 this impurity had been got rid of. 



To the difficult questions connected with the origin and formati 

 in considerable quantities, of a pigment, such as is here described, 

 source whence it is derived, and the manner in which it enters t! 

 urine, of which it is a constant constituent, it is, at present, im 

 sible to venture even u hypothetical answer ; and we may well conte: 

 ourselves for some time to come with the attempt to establish upon 

 firm basis the contention that the yellow colour of urine is not due 

 any of the baud-yielding pigments, but to a distinct yellow colou 

 matter, of negative spectroscopic properties, which may be ju 

 from its reactions to be a definite chemical entity. For the design 



