SULPHATE OF SODA. 

 Fig. 1. 



15 



which a stream of hydrogen is passed until it is com- 

 pletely reduced to metallic silver, which is then weighed. 



3. SULPHATE OF SODA. 

 NaO ; S0 3 -flOHO. 



For the determination of the water, a weighed quan- 

 tity of the salt is gradually and carefully heated in 

 a platinum crucible, until the whole of the water is 

 expelled, to insure which the heat is finally raised to 

 ignition. 



The sulphuric acid is determined by dissolving the 

 salt in water and precipitating with chloride of barium. 

 The liquid is then warmed, and must not be filtered 

 until the sulphate of baryta has completely separated. 

 The clear liquid is then poured upon the filter, without 

 the precipitate, which is stirred up with hot water, 

 again allowed to subside, the clear liquid being poured 

 upon the filter, and the precipitate once more treated 

 in the same way before it is thrown upon the filter, in 

 order that none may pass through the pores of the 



