274? Messrs. Allen and Pepys on the 
the exact weight of a given quantity of oxygene and carbonic 
acid gases, we resolved to examine for ourselves, whether the 
statements already given were quite correct, and accordingly 
made carbonic acid over mercury from Carrara marble and 
diluted sulphuric acid, which being tried with lime water in 
Pepys’s eudiometer, was all absorbed in 3 minutes except 1 
part in 100. We used two charges of lime water, though one 
would have been sufficient. 
A glass globe being exhausted by an excellent air pump, 
was exactly balanced on a beam sensible to a minute portion 
of a grain ; then being screwed upon one of the glass receivers 
of the mercurial gasometer previously filled with carbonic acid 
gas, 21 cubic inches entered. The globe was now increased in 
weight by 10,2 grains. In order to be certain we repeated the 
experiment, with exactly the same results. The 21 cubic 
inches were to be brought to the mean temperature and pres- 
sure, as the thermometer stood at 44 0 Fahrenheit, the ba- 
rometer 29,8 6. 
21 480)21,00 (0,043 6o° 
,68 add for temp. 16 44 
21,68 0,688 add for temp. 16 diff. 
Correction for Pressure. 
30 : 29,86 : : 21,68 : 21,58 
The volume therefore at mean temperature and pressure would 
have been 21,58 cubic inches. 
21,58 : 10,2 : : 100 : 47,26 
Consequently 100 cubic inches of carbonic acid gas at mean 
temperature and pressure weigh 47,26 grains. 
