20 



of silver chloride. The phosphate of silver may also 

 be throM^n down but the nitric acid dissolves it, keeping 

 it in solution. 



Evaporate carefully a few drops of urine upon a 

 glass slide, with a gentle heat over the flame. Octa- 

 hedral or rhombic crystals may form,— a compound of 

 sodium chloride and urea. Examine with the micro- 

 scope. (Fig. 5). 

 Sulphates. The sulphates are chiefly those of sodium 

 and potassium. Only a small amount of them enters the body 

 with the food, so that they are chiefly formed from the meta- 

 bolism of proteids in the body. The above are known as 

 ordinary sulphates. Another class known as the ethereal sul- 

 phates also exist. The proportion exists in the ratio of 10 of 

 the ordinary to 1 of the ethereal in man. In the horse the 

 proportion is about 2 of the ethereal to 1 of the ordinary. The 

 ethereal sulphates are formed by the combination of sulphuric 

 acid with organic bases such as phenol, skatol, etc., which 

 originate from putrefactive processes in the intestine. The 

 amount of ethereal sulphates is of importance in determining 

 whether or not the digestive processes are going on normally. 

 In general the sulphates are increased physiologically by the 

 ingestion of sulphur and its compounds ; nitrogenous food ; and 

 •conditions of increased metabolism. 



After acidulating the urine with hydrochloric acid 

 to prevent the precipitation of phosphates, add to a small 

 part of each urine, a little 2% barium chloride solution; 

 a precipitate of barium sulphate is formed, insoluble in 

 nitric acid. 



To separate the ethereal sulphates, mix 30 cc. of 

 urine with an equal bulk of "baryta" mixture. Stir and 

 filter. This removes the ordinary sulphates (as barium 

 sulphate), add 10 cc. of hydrochloric acid to the above 

 filtrate, and keep in the water bath at 100° C. for an 

 hour in the hood and then allow the ethereal sulphates 

 to settle. This may require some little time. (Baryta 

 mixture is prepared by making saturated solutions in 

 the cold, of barium nitrate and barium hydrate, and 

 adding two volumes of the hydrate to one volume of the 

 nitrate). 



