THE ORGANIC CONSTITUENTS OF THE URINE. 221 



phates are decomposed, with the liberation of the sulphuric acid, 

 which is then precipitated, together with the mineral sulphates, as 

 barium sulphate. To this end, 20 c.c. of a hot saturated solution of 

 barium chloride are added to the hot liquid. The mixture is kept 

 on a boiling water-bath until the precipitate has settled, when it is 

 collected on a small filter, washed with boiling water, then with hot 

 alcohol, and finally with ether. After incineration the filter ash is 

 deducted from the total weight. The result may be expressed in 

 terms of H 2 SO 4 , of SO 3 or S, by multiplying the weight of the barium 

 sulphate by 0.42015, 0.34301, or 0.13744, respectively. 



To determine the amount of mineral sulphates and of conjugate- 

 sulphates separately, 100 c.c. of urine are treated with an equal 

 volume of an alkaline solution of barium chloride, which consists of 

 two volumes of a solution of barium hydrate and one volume of the 

 chloride, both saturated at ordinary temperatures. The mineral sul- 

 phates are thus precipitated together with the phosphates and are 

 filtered off. One hundred c.c. of the filtrate, corresponding to 50 

 c.c. of the urine, are now strongly acidified with hydrochloric acid 

 and boiled. The conjugate sulphates are decomposed, and the lib- 

 erated sulphuric acid is thrown down, as above. The process is 

 then continued as described. The resulting value represents the 

 amount of sulphuric acid which was present in combination with 

 phenol, indoxyl, and skatoxyl. By deducting this value from the 

 total amount of sulphuric acid the mineral portion is ascertained. 



Test for Nitrates. To demonstrate the presence of nitrates, 

 200 c.c. of urine are treated with 30 to 40 c.c. of chemically pure, 

 concentrated sulphuric acid or hydrochloric acid, and distilled upon 

 a sand-bath. The distillate is received into a dilute solution of 

 caustic alkali. Owing to the presence of reducing substances in the 

 urine, the nitric acid is thus transformed into nitrous acid, and 

 passes over as such. The presence of nitrites may then be demon- 

 strated as usual. 



THE ORGANIC CONSTITUENTS OF THE URINE. 



The organic constituents of the urine comprise the normal end- 

 products of the nitrogenous metabolism of the body, various products 

 of albuminous putrefaction which have found their way into the 

 general circulation from the intestinal canal, and certain pigments 

 which are more or less intimately related to the normal blood-pig- 

 ment. In addition, traces of various other substances may be 

 encountered, the origin of which is obscure. Under pathological 

 conditions we meet with certain normal constituents of the blood 

 which generally do not appear in the urine as such, or occur in 

 infinitesimally small amounts, and also with various abnormal 

 products of metabolism, all of which will be considered in detail. 



