THE URINE. 383 



chloric acid, and then determining the sulphuric acid set free as 

 barium sulphate. A still better method is the following suggested 

 ,by SALKOWSKI: 



200 c. c. of urine are precipitated by an equal volume of a 

 barium solution which consists of 2 vols. barium hydrate and 1 vol. 

 barium-chloride solution, both saturated at the ordinary temper- 

 ature. Filter through a dry filter, measure off 100 c. c. of the 

 filtrate which contains only the ethereal sulphuric acid, treat with 

 10 c. c. hydrochloric acid of a specific gravity 1.12, boil for fifteen 

 minutes, and then warm on the water-bath until the precipitate 

 has completely settled and the supernatant liquid is entirely clear. 

 Wash with warm water and with alcohol and ether and proceed 

 according to the generally-prescribed method. The difference 

 between the ethereal sulphuric acid found and the total quantity 

 of sulphuric acid as determined in a special portion of urine is 

 considered as the quantity of sulphate-sulphuric acid. 



Nitrates occur in small quantities in human urine (SCHONBEIN), and they 

 probably originate from the drinking-water and the food. According to 

 WEYL and CITRON, the quantity of nitrates is smallest with a meat diet and 

 greatest with vegetable food. The average amount is about 42.5 milligrammes 

 per litre. 



Potassium and Sodium. The quantity of these bodies eliminated 

 by the urine by a healthy full-grown person on a mixed diet is, 

 according to SALKOWSKI, 3-4 grms. K 2 and 5-7.5 grms. Na a O. 

 The proportion of K to Na is ordinarily as 3:5. The amount 

 depends above all upon the food. In starvation the urine may 

 become richer in potassium than in sodium, which results from 

 the lack of common salt and the destruction of tissue rich in po- 

 tassium. The quantity of potassium may be relatively increased 

 during fever, while after the crisis the reverse is the case. 



The quantitative estimation of these bodies is performed by the 

 gravimetric methods as described in analytical works. 



Ammonia. Some ammonia is habitually found in human urine 

 and in that of carnivora. This ammonia may represent, as above 

 stated (page 338), on the formation of urea from ammonia, the 

 small amount of ammonia which, because of the excess of acids 

 formed by the combustion, as compared to the fixed alkalies, is 

 united with such acids and in this way excluded from the synthesis 

 to urea. These views are confirmed by the observations of Co- 

 RANDA, who found that the elimination of ammonia was smaller on 

 a vegetable diet and larger on a rich meat diet than when on a 



