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Mr. Tennant on the 
them being closed, was left undisturbed till the precipitate had 
fallen to the bottom, the solution having been previously heated 
that it might subside more perfectly. The clear liquor being 
found, by means of lime-water, to be quite free from fixed air, 
was carefully poured off from the calcareous precipitate.* The 
vessel which was used on this occasion was a glass globe, 
having a tube annexed to it, that the quantity of the fixed air 
might be more accurately measured. After as much quick- 
silver had been poured into the glass globe containing the cal- 
careous precipitate as was necessary to fill it, it was inverted 
in a vessel of the same fluid. Some marine acid being then 
made to pass up into it, the fixed air was expelled from the cal- 
careous earth; and in this experiment, in which two grains and 
a half of diamonds had been employed, occupied the space of a 
little more than 10.1 ounces of water. 
The temperature of the room when the air was measured, 
was at 55 0 , and the barometer stood at about 29.8 inches. 
From another experiment made in a similar manner with 
one grain and a half of diamonds, the air which was obtained 
occupied the space of 6.18 ounces of water, according to which 
proportion the bulk of the fixed air from two grains and a half 
would have been equal to 10.3 ounces. 
The quantity of fixed air which was thus produced by the 
diamond, does not differ much from that which, according to 
M. Lavoisier, might be obtained from an equal weight of char- 
coal. In the Memoirs of the French Academy of Sciences for 
* IT much water had remained, a considerable portion of the fixed air would have 
been absorbed by it. But by the same method as that described above, I observed, 
that as much fixed air might be obtained from a solution of mineral alkali, as by 
adding an acid to an equal quantity of the same kind of alkali. 
