468 



PRACTICAL PHYSIOLOGY 



The pink colour possessed by a deposit of urates is due to another 

 pigment uroerythrin. This pigment is never excreted in large amount, 

 but it possesses in high degree a colouring power. If a pink urate 

 deposit be dissolved in warm water the urates may be precipitated 

 by saturation with ammonium chloride carrying down the pigment. 

 This may now be extracted with alcohol, and on shaking the alcoholic 

 solution with chloroform to which one drop of acetic acid has been 



Fro. 256. 



1. Acid urobilin In strong solution. 



2. Urobilin precipitated by acid from its alkaline solution and partially redissolved. 

 so-called E-band spectrum. 



3. Uroerythrin. 



4. Uroerythrin in pink urate sediments. 



The 



added the pigment passes into the chloroform. It now gives the 

 spectrum seen in Fig. 256, 3. If the pink urate deposit be simply 

 dissolved in warm water the spectroscopic appearance is different, as 

 represented by Fig. 256, 4. 



Haematoporphyrin is normally present in very small amount in 

 urine. After certain drugs it may be present in comparatively large 

 amounts. Even in acid urine it is present in the condition in which 

 it shows the so-called alkaline spectrum (p. 345, Fig. 231, 11). 



