SULPHATES. 765 



greater part is formed by the burning within the body of the proteins 

 which contain sulphur, and it is chiefly this formation of sulphuric acid 

 from the proteins which gives rise to the previously mentioned excess 

 of acids over the bases in the urine. The quantity of sulphuric acid 

 eliminated by the urine amounts to about 2.5 grams H^SCU per day. 

 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:H2SO4 is about 5:1. A complete 

 parallelism can hardly be expected, as in the first place a part of the sul- 

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

 small proportion of sulphur in different protein bodies undergoes greater 

 variation 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 J3-sulphuric acid. 



The quantity of total sulphuric acid is determined in the following 

 way, but at the same tin^e 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 

 boiling precipitate with 2 cc. of a saturated BaC^ 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 BaCb 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 l : 



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. 



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



