216 QUANTITATIVE ANALYSIS. 



acid added, and heated till colorless. The ammonium nitrate 

 is added in three portions after cooling each time. When 

 cold, make alkaline with ammonia and acidify with acetic 

 acid. In case no precipitate (of ferric phosphate) is formed, 

 the phosphoric acid may be titrated with the uranium solu- 

 tion; otherwise it must be determined gravimetrically. We 

 may also in any case acidify with nitric acid and precipitate 

 with ammonium molybdate solution. 



Pfeiffer and Scholz (Deutsches Arch. f. klin. Med. 63, 373) 

 recommend to heat 0.5 to 1.0 g. of the dried fseces with 10 cc. 

 of sulphuric acid and 5 g. of potassium sulphate and to pre- 

 cipitate the diluted solution with ammonia and magnesia 

 mixture. The precipitate is filtered off, dissolved in dilute 

 acetic acid, together with the ammonium magnesium phos- 

 phate clinging to the beaker (the volume of the solution 

 should not exceed 50 cc.) ; the solution is then neutralized 

 with caustic soda, 5 cc. of acetic acid mixture added (see 

 under Urine), and titrated with the uranium solution (the 

 method does not take into consideration the ferric phosphate, 

 which is seldom entirely absent; the analyses given, how- 

 ever, show concordant results). 



7. Determination of the Total Sulphur. Fuse about 2 

 g. with 30 g. of the oxidizing mixture, then proceed as directed 

 in the determination of sulphur in the urine, page 207. 



