542 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



(2) Ethereal Sulphates. 



200 c.c. of urine are placed in a beaker and 100 c.c. of 10 per cent, barium 

 chloride solution are added. The mixture is stirred and set aside for 24 

 hours. The clear supernatant liquid is decan;ed into a dry beaker and filtered. 

 150 c.c. of the filtrate (= 100 c.c. of urine) are measured into a 400 c.c. 

 conical flask, 10-15 c.c. of concentrated hydrochloric acid and 10-15 c - c - f 

 4 per cent, potassium chlorate solution are added. The mixture is heated to 

 boiling. The remainder of the operation is the same as above (i).; 



(3) Total Sulphates. 



(Denis' modification of Benedict's process.) 



25 c.c. of urine are placed in a porcelain basin, 4-5 cm. in diameter, 

 and evaporated to dryness with 5 c.c. of a copper nitrate oxidising solution. 1 

 The residue is first gently heated with a small flame and finally to redness for 

 10-15 minutes. The black residue is dissolved in 10-15 c - c - of 10 per cent, 

 hydrochloric acid, which is gently warmed. The solution is transferred to a 

 200 c.c. conical flask, diluted to TOO or 150 c.c. and precipitated with 25 

 c.c. of 10 per cent, barium chloride solution as above. 



A blank must be made with the oxidising solution. 



Volumetric Estimation. 



The inorganic and ethereal sulphates may be estimated by the 

 volumetric method pror5bsed by Rosenheim and Drummond in 1913. 

 It depends upon the insolubility of benzidine sulphate in very dilute 

 hydrochloric acid. Excess of acid hinders the precipitation. 



(i) Inorganic Sulphates. 



2$ c.c. of urine are pipetted into a clean 250 c.c. flask or beaker 

 and acidified to congo red with 1-2 c.c. of dilute hydrochloric acid; 

 100 c.c. of benzidine chloride solution 2 are now added. After 10-15 

 minutes the benzidine sulphate is filtered off through a small filter 

 and washed free from acid with water saturated with benzidine 

 sulphate. The precipitate, together with the paper, is returned to the 

 flask or beaker, about 50 c.c. of water are added and the contents of 

 the flask are heated to about 80. A few drops of phenolphthalein are 

 put in and the solution is titrated with -iN sodium hydrate until it is 

 red in colour. 



The result is in c.c. of a iN H 2 SO 4 (i c.c. = 0*0049 g m - H 2 SO 4 ). 



1 25 gm. copper nitrate + 25 gm. sodium chloride + 10 gm. ammonium nitrate per 

 100 c.c. 



3 This is prepared by rubbing 4 gm. of benzidine into a fine paste with about 10 c.c. of 

 water and transferring it with about 500 c.c. of water into a 2-litre flask. 5 c.c. of concen- 

 trated hydrochloric acid are added and the volume made up to 2000 c.c. with water. (100 

 c.c. of this solution will precipitate *i gm. H 2 SO 4 .) 



