726 URINE. 



As the sulphuric acid chiefly originates from the proteins, it follows that 

 the elimination of sulphuric acid and the elimination of nitrogen runs 

 almost parallel, and the relation N : H 2 SO 4 is about 5:1. A complete par- 

 allelism can hardly be expected, as in the first place a part of the sulphur 

 is always eliminated as neutral sulphur, and secondly because the small 

 proportion of sulphur in different protein bodies undergoes greater varia- 

 tion as compared with the large proportion of nitrogen contained therein. 

 In general the elimination of nitrogen and sulphuric acid under normal 

 and under diseased conditions seems to run parallel. Sulphuric acid 

 occurs in the urine partly preformed (sulphate-sulphuric acid) and partly 

 as ethereal-sulphuric acid. The first is designated as A- and the other 

 as 5-sulphuric acid. 



The quantity of total sulphuric acid is determined in the following 

 waj/, but at the same time the precautions' described in other works 

 must be observed. 100 cc. of filtered urine is treated with 5 cc. of con- 

 centrated hydrochloric acid and boiled for fifteen minutes. While boil- 

 ing precipitate with 2 cc. of a saturated BaCl2 solution, and warm for 

 a little while until the barium sulphate has completely settled. The 

 precipitate must then be washed with water and also with alcohol and 

 ether (to remove resinous substances), and then treated according to 

 the usual method. 



The separate determination of the sulphate-sulphuric acid and the 

 ethereal-sulphuric acid may be accomplished, according to BAUMANN'S 

 method, by first precipitating the sulphate-sulphuric acid by BaCl 2 from 

 the urine acidified with acetic acid, then decomposing the ethereal- 

 sulphuric acid by boiling after the addition of hydrochloric acid, and 

 finally determining the sulphuric acid set free as barium sulphate. A 

 still better method is the following, suggested by SALKOwsKi 1 : 



200 cc. of urine are precipitated by an equal volume of a barium solu- 

 tion which consists of 2 vols. barium hydrate and 1 vol. barium-chloride 

 solution, both saturated at the ordinary temperature. Filter through 

 a dry filter, measure off 100 cc. of the filtrate which contains only the 

 ethereal-sulphuric acid, treat with 10 cc. of 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. Filter and 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 taken to be the quantity of sulphate-sulphuric acid. 



FOLIN 2 has suggested a method for estimating the sulphate-sul- 

 phuric acid as well as the ethereal-sulphuric acid, and also the total 

 sulphur, which is unlike the ordinary methods. 



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

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



1 Baumann, Zeitschr. f. physiol. Chem., 1; Salkowski, Virchow's Arch., 79. 



2 Journ. of Biol. Chem., 1, and Arner. Journ. of PhysioL, 13. 



