THE JOURNAIv OF PHARMACOLOGY. 27 



view of the fact that some of the chlorine may be in organic combination, 

 and would therefore not be taken into account by Volhard's method, this 

 method of procedure would seem to yield more accurate results. 



Execution of method : 10 cc. or preferably 10 gm. of urine are evapor- 

 ated in a platinum crucible with 2 parts of sodium carbonate and i part of 

 sodium nitrate and then carefully ashed. The residue thus obtained is 

 extracted with distilled water, acidified with nitric acid, and the solution 

 thus obtained is carefully neutralized with pure sodium carbonate. To 

 this solution a few drops of a solution of potassium chromate (10 gm. 

 K2CRO4 — 100 cc. HoO) are added, and the mixture titrated with deci- 

 normal silver nitrate solution until a permanent red tint develops. 

 (Method of Mohr.) 



N 

 I cc. - AgNOgV.S. =0.003537 S^- chlorine. 



0.005837 gm. sodium chloride. 



This method is based on the fact that when silver nitrate is added to a 

 neutral solution of a chloride, a precipitate of silver chloride is formed. 

 When all the chlorine has united with silver, then the next drop of silver 

 solution added will unite with the potassium chromate, forming red silver 

 chromate. Magnesia is sometimes added in order to make the red color 

 more apparent ; if this is done care must be taken that it is free from 

 chlorides. 



The fused mass obtained as above may also be extracted with distilled 

 water acidified with nitric acid, and then treated as in the Volhard method. 

 This procedure is found to be even more accurate than the Mohr method. 

 The method of ashing is also particularly serviceable in case of urine con- 

 taining albumin. If iodides or bromides are present these methods must 

 be modified. As however the estimation of iodine and bromine in the 

 presence of chlorine is seldom necessary in urine analysis, the methods by 

 means of which this may be accomplished need not be considered here. 



Sulphates (H2SO4, SO3). 



Sulphur as found in urine is divisible into two groups: first, completely 

 oxidized or acid sulphur, and second, partially oxidized, or neutral sul- 

 phur. To the latter group, all the sulphur containing bodies, except 

 sulphuric acid, belong. Among such bodies may be classified sulpho- 

 cyanates, thiosulphates, cystin, taurin, etc. Some of these, as for in- 

 stance, sulphocyanates and thiosulphates, are readily oxidized, others are 

 only oxidized with difficulty. In the urine of the dog the neutral sulphur 

 constitutes about 30 ;» of the total sulphur eliminated, while in urine of 

 man it averages only about one-half of this amount. Sulphuric acid be- 

 longs to the first group, namely, to the group containing the completely 

 oxidized sulphur. This group is again subdivided, as follows : 



