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ammoniac diffolves in coniiderable quantity in weak 
ipirits of fal ammoniac made with lime, and the 
folution differs in no refpedt from the fpirits made with 
fixed alcali. This is a convenient way of procuring 
the mild fpirits of fal ammoniac, as thofe made with 
fixed alcali are feldom to be met with in thefhops. 
Experiment XIV. 
The quantity of fixed air contained in pearl afhes 
was tried, by mixing a folution of pearl allies with 
diluted oil of vitriol, in the fame manner as was ufed 
for volatile fal ammoniac. As much of the folution 
was ufed as contained 328- grains of dry pearl allies. 
The lofs of effervefcence was 90 grains. The mix- 
ture, which was perfectly neutralized, being then 
added to a fufficient quantity of lime water, in order 
to fee whether it contained any fixed air, a precipitate 
was made, which being dried weighed 84. grains. 
Therefore, if we fuppofe this precipitate to contain as 
much fixed air as an equal weight of marble, which 
I am well allured cannot differ very confiderably from 
the truth, the fixed air therein is 3 4 grains, and confe- 
quently the air in 3284. grains of the pearl afhes, is 
934 - grains, /. e. .VVo oi their weight. 
By another experiment tried in the fame way, they 
appeared to contain V-oVo °f their weight of fixed air. 
1 558 grains of the pearl allies were found to faturate 
as much acid as 1000 grains of marble. Therefore 
this parcel of pearl allies contains more air in propor- 
tion to the quantity of acid that it can faturate, than 
marble does, in the proportion of 109 to 100. 
Experi- 
