ANALYSIS OF URINE 543 



(2) Inorganic + Ethereal Sulphates. 



25 c.c. of urine as above are boiled gently for 15-20 minutes 

 with 20 c.c. of dilute hydrochloric acid to hydrolyse the ethereal 

 sulphates. The solution is cooled, neutralised and again acidified 

 to congo red ; 100 c.c. of benzidine chloride solution are added. The 

 remainder of the process is as described under inorganic sulphates. 



(3) Ethereal Sulphates. 



The amount of ethereal sulphates is the difference between the 

 amounts found in (2) and (i). 



(4) Total Sulphates. 



10 c.c. of urine are evaporated to dryness in a small basin, 5-7 cm. 

 in diameter, on a water-bath with 5 c.c. of Denis-Benedict's oxidising re- 

 agent (p. 542). The basin is covered with a clock glass and the dry residue 

 is carefully heated over a flame until the copper nitrate is completely decom- 

 posed and converted into copper oxide. The basin is allowed to cool and 

 the contents are dissolved in 10 c.c. of dilute hydrochloric acid and 10 c.c. 

 of water. The solution is neutralised, made very faintly alkaline with caustic 

 soda and warmed. The precipitate of copper oxide is filtered off and 

 thoroughly washed. To the filtrate, now of a volume of about 25 c.c., are added 

 i-2 c.c. of dilute hydrochloric acid and 100 c.c. of benzidine chloride solu- 

 tion. The benzidine sulphate is filtered off and treated as under (i). 



(5) Neutral Sulphur. 



The difference between the amounts found in (4) and (2) is the 

 amount of neutral sulphur. 



