UEINE 153 



THE INORGANIC CONSTITUENTS OF URINE 



The inorganic or mineral constituents of urine are chiefly chlorides, 

 phosphates, sulphates, and carbonates ; the metals with which these 

 are in combination are sodium, potassium, ammonium, calcium, and 

 magnesium. The total amount of these salts excreted varies from 19 

 to 25 grammes daily. The most abundant is sodium chloride, which 

 averages in amount 10 to 13 grammes per diem. These substances 

 are derived from two sources first from the food, and secondly as the 

 result of metabolic processes. The chlorides and most of the phos- 

 phates come from the food ; the sulphates and some of the phosphates 

 are a result of metabolism. The sulphates are derived from the 

 changes that occur in the proteins ; the nitrogen of proteins leaves the 

 body chiefly as urea ; the sulphur of the proteins is oxidised to form 

 sulphuric acid, which passes into the urine in the form of sulphates. 

 The excretion of sulphates, moreover, runs parallel to that of urea. 

 Sulphates, like urea, are the result of exogenous protein metabolism ; 

 endogenous metabolism so far as sulphur is concerned is represented 

 in the urine partly as ethereal sulphates, but chiefly by less fully 

 oxidised compounds of sulphur. The chief tests for the various salts 

 have been given in the practical exercises at the head of this lesson. 



Chlorides. The chief chloride is that of sodium. The ingestion of 

 sodium chloride is followed by its appearance in the urine, some on the 

 same day, some 011 the next day. Some is decomposed to form the 

 hydrochloric acid of the gastric juice. The salt, in passing through 

 the body, fulfils the useful office of stimulating metabolism and 

 excretion. 



Sulphates, The sulphates in the urine are principally those of 

 potassium and sodium. They are derived from the metabolism of 

 proteins in the body. Only the smallest trace enters the body with the 

 food. Sulphates have an unpleasant bitter taste (for instance, Epsom 

 salts) ; hence we do not take food that contains them. The sulphates 

 vary in amount from 1'5 to 3 grammes daily. 



In addition to these sulphates there is a small quantity of 

 sulphuric acid comprising about one-tenth of the total which 

 is combined with organic radicals ; the compounds are known as 

 ethereal sulphates, and they originate mainly from putrefactive 

 processes occurring in the intestine. The most important of these 

 ethereal sulphates are phenyl sulphate of potassium and indoxyl 

 sulphate of potassium. The latter originates from the indole formed 

 in the intestine, and as it yields indigo when treated with certain 



