OF SOME SALTS OF SODA. 95 
the plan of placing the salt, the object of expe- 
riment, under an exhausted air pump receiver 
along with a vessel of concentrated sulphuric 
acid. By this method we avoid the inconve- 
niences consequent upon the watery fusion 
which the salts undergo by the immediate ap- 
plication of heat. 
One hundred grains of crystals of carbonate 
of soda put under an exhausted receiver with a 
vessel of sulphuric acid lose in a few days (tem- 
perature ranging from 39° to 45°) 56.8 grains of 
water. By allowing the salt to remain under 
the receiver longer, no further loss is sustained: 
but, by exposing the 43.2 grains of remaining 
salt to ared heat 6.2 grains of water are expelled, 
and 37 grains of anhydrous salt are left. This 
anhydrous salt being put under an exhausted 
receiver with a vessel of water instead of sul- 
phuric acid, rapidly gains water; and in two or 
three days becomes of the same constitution as 
the crystals, its weight being 100 grains if no 
portion has been lost in the manipulations. 
One hundred grains of crystals of sulphate of 
soda by the exhausted receiver and sulphuric 
acid lose in a few days (temperature about 45°) 
56.2 grains of water: the salt remaining is 
