SODA AND SODIUM. 59 



grain. This excess of water is mechanically 

 lodged between the plates of the crystals ; it 

 may be got rid of by reducing the crystals to 

 powder, and pressing them between two folds of 

 blotting paper. But, as the salt is very easily 

 rendered anhydrous, it is better to employ it for 

 the experiment which I am going to describe, in 

 that state. It may be rendered anhydrous by 

 placing it for some hours, in the vacuum of an 

 air-pump, along with an open vessel of sulphuric 

 acid or by exposing it to a moderate heat in a 

 platinum crucible. 



Nine grains of anhydrous sulphate of soda, and 

 13'25 grains of chloride of barium, were dis- 

 solved in separate portions of distilled water. 

 The two solutions being mixed, a double decora 

 position took place, and sulphate of barytes pre- 

 cipitated in the state of a white powder. As 

 soon as the liquid had become transparent, it was 

 tested with sulphate of soda and muriate of ba- 

 rytes, but was not rendered opalescent, nor in 

 the least altered, by either of these reagents. It 

 therefore contained no sensible quantity of ba- 

 rytes or sulphuric acid. From this experiment, 

 it follows, that the sulphuric acid in 9 grains of 

 anhydrous sulphate of soda is just saturated by 

 the barytes from 13-25 grains of chloride of bari. 

 urn. Now, this quantity we know is exactly 5 

 grains ; consequently, anhydrous sulphate of 

 soda is composed of 



