624 
THE CHEMISTRY OF THE URINE. 
its solutions are decolorised by light ; and (3) its colour reactions 
with the caustic alkalies and mineral acids. The pigment invariably 
associates itself with urates during their precipitation ; either when they 
separate naturally from a urine containing it, or when they are arti- 
ficially added to its pure solutions, and are allowed afterwards to separate. 
£. b. F. 
Fi<;. 57. — Chart of spectra. 
1. Arid luomatoporphyrin. 
2. Alkaline hajmatoporphyrin. 
3. HsBmatoporphyrin as found in urate sediments. 
4. Acid urobilin — concentrated. 
f>. Acid urobilin— dilute. 
6. The E band spectrum. 
7. Uroerythrin. 
S. Urorosein concentrated— on dilution the band 
shrank rapidly from redward end. 
It apparently forms a loose compound with the urates, as a special 
absorption-spectrum is seen when light passes through the pink pre- 
cipitate, differing from that proper to solutions of the pigment (Garrod). 
The best solvent of uroerythrin is amylic alcohol ; acetic ether is but 
little inferior, and the pigment is also soluble in alcohol, chloroform, and 
