&n the fpectfic Gravities, he. of Saline Sutfances.. 191 
The fpecific gravity of the cryhallized. mineral alkali; 
weighed in aether 1 found to be 1 ,42 1 . 
OF THE VOLATILE ALKALI. 
It is not pofiible by the old chymical methods to find the 
proportion of the ingredients in volatile alkalies, whether in a 
liquid or in a concrete hate; feeing that, though it may be 
Separated from fixed air, yet it cannot from water, on account 
of its extreme volatility. Then to find this proportion we muh 
recur to the experiments of Dr. Priestley, who by his new ana- 
lyfis produced this alkali free from the aerial acid and water in 
the form of air: and in the third volume of his Obfervations, 
p 294.. informs us*, that i a meafures of alkaline air take up, 
and are fat u rated by, 1 meafure of fixed air. Let us luppofe 
the meafure to contain ion cubic inches; then 185 cubic 
inches of alkaline air take up iqo of fixed air; but 185 cubic 
inches of alkaline air weigh, at a medium, 42,55 gr. ; and 
100 cubic inches of fixed air weigh 57 gr. ; then 100 gr. of 
pure volatile alkali, free from water, take up 134 of fixed air. 
On expelling its aerial acid from a parcel of this alkali in a 
concrete hate, and formed by fublimation, I found 100 gr. of 
it to contain 53 of fixed air, and therefore, according to the 
preceding reafoning, 39,47 of real alkali and 7,53 of water 
per cent* 
Saturating a folution of this alkali with the vitriolic, nitrous, 
and marine acids, I found, that 100 gr. of the mere alkali 
take up 106 of mere vitriolic acid, 115 of the nitrous, and 
130 of the.marine* 
The 
