C r 74 ] 
abforbed fomewhat more than 1 - of the air firfl 
thrown into the bladder, it would not abforbany more: 
but, on prefling the remaining air out of the bladder, 
and fupplying its place with frefli fixed air, a good 
deal of this new air was abforbed. I cannot, how- 
ever, i'peak pofitively as to this point; as I am not 
certain whether the apparatus was perfectly air- 
tight*. 
Thefe cryflals do not in theleaft attrad the moifture 
of the air ; as I have kept fome, during a whole win- 
ter, expofed to the air in a room without a fire, with- 
out their growing at all moift or increaflng in 
weight. 
Being held over the fire in a glafs veflel, they did 
not melt as many falts do, but rather grew white and 
calcined. 
They diflolve in about four times their weight of 
water when the weather is temperate, and difloive in 
greater quantity in hot water than cold. 
It was found, by the fame method, that was made 
'ule of for the volatile fal ammoniac, that thefe cryflals 
contain -V-oV °f their weight of fixed air, and that 
2°3 5 grains of them faturate as much acid as 1000 
grains of marble. Therefore thefe cryflals contain 
more air in proportion to the quantity of acid they 
* Pearl afhes deprived of their fixed air, i. c. fope leys, will 
abforb the whole of the air difcharged from marble ; as I know 
by experience. But yet it is not improbable* but that the fame 
alcali, when near faturated with fixed air, may be able to abforb 
only fome particular part of it. For as it has been already fhewn, 
that part of the air difcharged from marble is more loluble in 
water than the reft; fo it is not unlikely, but that part of it may 
have a greater affinity to fixed alcali, and be abforbed by it in 
greater quantity than the reft. 
faturate. 
