1308 UROBILIN UROERYTHRIN. 



A solution of urobilin may be readily obtained as follows. 

 Urine is made alkaline with ammonia and then saturated with 

 neutral ammonium sulphate. The precipitate thus formed is 

 collected on a filter freed by pressure from adhering fluid, dried 

 in the air till free from ammonia and extracted with absolute 

 alcohol. This solution is yellowish-brown or yellow if more 

 dilate, and shews a strong green fluorescence. If made acid 

 with hydrochloric acid the colour deepens and the fluorescence 

 disappears. Alkaline solutions are yellow or yellowish-green, 

 according to the concentration. The fluorescence is usually 

 increased by the addition of zinc chloride, the solutions ap- 

 pearing rose-coloured by transmitted light and bright green by 

 reflected. 



Spectra of urobilin. Neutral or alkaline alcoholic solutions 

 shew one absorption band between b and F. In alkaline solu- 

 tion the band is frequently very faint, but may be more strongly 

 marked after the addition of zinc chloride. In acid solutions 

 a similar band is seen, situated however in this case slightly 

 more towards the violet end of the spectrum. 



In fevers the urine contains additionally a colouring sub- 

 stance to which the name of febrile urobilin has been given. 

 It is closely related to normal urobilin, but differs in the red 

 colour of its acid alcoholic solution as compared with the yellow 

 of ordinary urobilin, and this solution shews an absorption band 

 in the yellowish-green of the spectrum on the red side of the 

 line E. 



The colouring power of urobilin is inconsiderable, hence 

 the normal colour of urine is chiefly due to some other pigment 

 of which as yet but little is definitely known. It has been 

 called urochrome. 



2. Uroerythrin. 



This is a pigment of which but little is known. It is 

 regarded as the colouring substance of certain bright red (pink) 

 urinary deposits and as possibly occurring in the highly coloured 

 urines of rheumatism, etc. It appears to be an amorphous 

 reddish substance, with an acid reaction, slowly soluble in 

 either water, alcohol or ether, readily soluble in amyl-alcohol. 

 Treated with caustic alkalis it turns green, more particularly 

 when in the solid form. In alcoholic solution obtained by boil- 

 ing pink urates with alcohol it shews two ill-defined absorption 

 bands between D and F. 



3. Urohaematoporphyrin. 



This pigment is described as occasionally occurring in cer- 

 tain pathological urines as of acute rheumatism, Addison's 

 disease, etc., and receives its name from certain resemblances of 



