96 EFFLORESCING PROPERTIES 
anhydrous, and weighs 43.8 grains ;—it loses 
no weight by exposure to a red heat. By e po- 
sure for a few days under the exhausted receiver 
with a vessel of water it becomes of the same 
constitution as the crystals, and weighs 100 
grains. 
One hundred grains of crystals of phosphate 
of soda by the exhausted receiver and sulphuric 
acid lose in a few days (temperature about 45°) 
60.35 grains of water. By allowing the salt to 
remain under the receiver longer, no further 
loss is sustained; but, by a red heat the 39.65 
grains of remaining salt are reduced to 37.1 
grains. This anhydrous pyro-phosphate being 
put under the exhausted receiver with a vessel 
of water gains water rapidly, and in a day or 
two weighs 66 grains; after which it gains no 
more weight :—but if the salt when not calcined, 
but merely dried by the action of the exhausted 
receiver and sulphuric acid till its weight is 
39.65 grains, is submitted to the same treatment 
it gains water till its weight is again 100 grains. 
The crystals of all these salts by losing their 
water lose their transparency and their hard- 
ness ; but when they are allowed to regain their 
water, whether from the open atmosphere or 
