URINE. 107 



4. A potassium sulphocyanide solution of which 2 c.c. 

 corresponds to 1 c.c. of the known AgN0 3 solution. 



Method: Prepare a clean and dry graduate. By means 

 of a pipette measure off accurately 5 c.c. of urine and run it 

 into the graduate. Add 3 c.c. of the HN0 3 and dilute with 

 water to about 25 c.c. Then allow exactly 10 c.c. of the 

 known AgN0 3 solution to flow in. Add water until the 

 volume equals 50 c.c. ; then mix thoroughly. Transfer this 

 now to a clean and dry beaker and clean and dry the gradu- 

 ate again. Prepare also a clean and dry funnel with paper 

 and filter the mixture in the beaker into the graduate. When 

 25 c.c. of a water-clear nitrate has passed through remove the 

 funnel to a test-tube. Add 10 drops of the iron alum to the 

 graduate and titrate with the known potassium sulphocya- 

 nide until the first tinge of pink appears in the solution. 



Calculate the amount of chlorine or Nad in the 5 c.c. of 

 the urine used, and then in the 24-hour sample. 



SULPHATES =S0 3 . 



A variable fraction (80 to 90 per cent) of the total sulphur 

 of the urine exists in a completely oxidized form as the salts of 

 sulphuric acid, usually denoted and calculated as S0 3 . Of the 

 total S0 3 , about nine-tenths is combined with bases (preformed) 

 anc? one-tenth with aromatic radicles (conjugate sulphates). 

 The "organic " sulphur appears as taurine, cystine, KSCN, etc. 



Since the food contains merely minimum quantities of 

 S0 3 , that found in the urine must originate as a product 

 of protein metabolism, in which the sulphur of the molecule 

 becomes oxidized. Thus it is that ordinarily the S0 3 output 

 mav be considered as indicative of the amount of protein 

 burned in the body. About 1.5-3.0 grms. (average 2.5 

 grms.) SOs are excreted during 24 hours. 



