154 ESSENTIALS OF CHEMICAL PHYSIOLOGY 



reagents it is sometimes called indie an. It is very important to 

 remember that the indican of urine is not the same thing as the 

 indican of plants. Both yield indigo, but there the resemblance 

 ceases. 



The equation representing the formation of potassium phenyl- 

 sulphate is as follows : 



C,,H 5 OH + S0 2 /f = 



[phenol] [potassium [potassium [water] 



hydrogeu sulphate] phenyl-sulphate] 



The formation of potassium indoxyl-sulphate may be represented 



CH 



as follows : Indole, C 6 H 4 /\CH on absorption is converted 



NH 

 C.OH 



into indoxyl : C ( 



>H 



Indoxyl then interacts with potassium hydrogen sulphate as 

 follows : 



[indoxyl] [potassium [potassium [water] 



hydrogen sulphate] iudoxyl-sulphate] 



The formation of such sulphates is important ; the aromatic sub- 

 stances liberated by putrefactive processes in the intestine are 

 poisonous, but their conversion into ethereal sulphates renders them 

 innocuous. (For tests for indoxyl in urine see Advanced Course, 

 Lesson XXVI.) 



Carbonates. Carbonates and bicarbonates of sodium, calcium, 

 magnesium, and ammonium are present in alkaline urine only. They 

 arise from the carbonates of the food, or from vegetable acids (malic, 

 tartaric, &c.) in the food. They are, therefore, found in the urine of 

 herbivora and vegetarians, whose urine is thus rendered alkaline. 

 Urine containing carbonates becomes, like saliva, cloudy on stand- 

 ing, the precipitate consisting of calcium carbonate, and also phos- 

 phates. 



Phosphates. Two classes of phosphates occur in normal 

 urine : 



(1) Alkaline phosphates that is, phosphates of sodium (abundant) 

 and potassium (scanty). 



