[ 168 ] 
in the cylinder was about 1 160 grain meafures : the 
excefs of weight of which quantity of fixed air above 
an equal bulk of common air is .1 grains. Therefore 
the quantity ot moifture condenfed in the filtering 
paper is one grain, or about T i- T part of the weight of 
the air difcharged. 
As water has been already fhewn to abforb fixed 
air, it feemed not improbable, but what there might 
be fome fixed air contained in the folution of marble 
in fpirit of fait; in which cafe the air difcharged, 
during the effervefcence, would not be the whole of 
the fixed air in the marble. In order to fee whether 
this was the cafe, I poured fome of the folution into 
lime water. It made fcarce any precipitate; which, 
as the acid was intirely faturated with marble, it would 
certainly have done it the folution had contained any 
fixed air. It appears therefore from this experiment, 
fir ft, that marble contains ----- of its weight 
3114. icoo 
of fixed air; and fecondly, that the quantity of 
moifture, which flies off along with the fixed air in 
effervefcence, is but trifling ; as I imagine that the 
greateft part of what did fly off mu ft have been 
condenled in the filtering paper. 
Bv another experiment tried much in the fame way, 
marble was found to contain -AW of its weight ot 
fixed air. 
Experiment XI. 
Volatile fal ammoniac diffolves with too great 
rapidity in acids, and makes too violent an effer- 
vefeence, to allow one to try what .quantity of fixed 
I air 
