1894.] of the Yellow Colouring Matter of the Urine. 403 



tions it was not possible to assign to it even an approximate limit. 

 There was no increase of the absorption in the position of the urobilin 

 band. 



Treatment with zinc chloride and ammonia did not produce any 

 fluorescence. 



The alcoholic solutions always showed the same rich yellow or 

 orange tint, and could be kept for a long time without undergoing 

 any appreciable change ; but aqueous solutions kept in stoppered 

 bottles tended to assume a brown tint on standing, even when dilute, 

 and this change was precipitated by evaporation or warmth. In this 

 respect my product behaved just like urochrome. 



The tendency of the aqueous solutions to undergo this change could 

 be restrained by the addition of a little ammonia. 



Alkalies did not appreciably alter the tint of dilute solutions, but 

 more concentrated ones were slightly browner when alkaline than in 

 the neutral condition. 



Small additions of mineral acid produced no immediate change, 

 but larger quantities quickly changed the colour to a reddish-brown. 



Solutions of the pigment were decolorised by nascent hydrogen 

 produced by the action of hydrochloric acid upon zinc. This is only 

 to be expected, seeing that it is a known fact that the urine is itself 

 decolorised by similar treatment.* The destroyed colour was not 

 restored by hydrogen peroxide. 



Action of Mineral Acids upon the Pigment. 



iolutions of the yellow pigment when warmed with nitric acid re- 

 mained clear, but took a distinctly brighter yellow tint. On the 

 addition of ammonia to alkalinity the yellow colour changed to a rich 

 orange, the changes of tint being exactly similar to those which con- 

 stitute the xanthoproteic reaction. This reaction seemed to be due to 

 a change in the pigment as a whole, and not to any traces of impurity 

 present. 



Heated over the water bath with the addition of sulphuric or 

 hydrochloric acid, the changes observed were uniform with all speci- 

 mens of the indigo-free pigment which were subjected to this 

 treatment, and were the same whichever of the two acids was 

 employed. 



The colour of the liquid quickly changed to reddish-brown, and on 

 evaporation to dryness a nearly black residue was left. This residue, 

 when treated with water, yields an orange-coloured solution, resem- 

 bling the original liquid in colour, but darker in tint. This aqueous 

 extract left on evaporation a brown residue, which was scarcely soluble 



alcohol, but which communicated a yellow colour to chloroform. 



* Salkowski imd Leube, ' Die Lelire vom Harn,' 1882, p. 14. 

 VOL. LV. 2 F 



