OF SOME SALTS OF SODA. 85 
as well as I thought possible, into a watch glass 
and left them exposed to the atmosphere of the 
same room. By the first two days exposure a 
loss of 24 grains was sustained ; but, afterwards, 
though the exposure was continued till the 3rd 
November and the weighing repeated every day, 
neither loss of weight nor efflorescence was per- 
ceived; but the crystals remained transparent. 
Of course the 2} grains of loss in this case also 
must only be the consequence of using imper- 
fectly dried crystals: indeed, as a proof of this 
may be noticed the fact that while this experi- 
ment was going on I placed in exposure to the 
same atmosphere some anhydrous sulphate, and 
it gained weight. The quantity of anhydrous 
sulphate exposed was 20 grains; and in 86 days 
it gained 25.4 grains of water, whereby it was 
rendered of about the same constitution as the 
crystallized salt. 
When I became aware what were likely to be 
the results of the experiments I have related, my 
object was to repeat them in an atmosphere of 
greater drying power. I therefore left exposed 
to the atmosphere of a room in which a moderate 
- fire was regularly kept, 20 grains of crystals of 
Sulphate of Soda, 20 grains of crystals of Car- 
bonate of Soda, and 20 grains of anhydrous 
