CARBON. 143 



spar, supposing the barometer to stand at 30 

 inches, the thermometer at 60, and the gas to 

 be perfectly dry, amounts, from a mean of two 

 experiments, both made with very great care, to 

 94*426 cubic inches. 



Now, we have seen that the weight of this vo- 

 lume of carbonic acid gas is 44 grains. Conse- 

 quently, 100 cubic inches of carbonic acid gas 

 must weigh 46-5973 grains; but 100 cubic 

 inches of air weigh 30%5 grains. We have, 

 therefore, 30*5 : 46-5973 : : 1 : 1 -52778 = speci- 

 fic gravity of carbonic acid gas. 



Thus the specific gravity of carbonic acid gas, 

 determined by ascertaining the volume of a given 

 weight, amounts to 1 -52778' By means of a 

 nonius and a microscopic sight, I was enabled to 

 measure the volume of gas with precision to the 

 thousandth part of a cubic inch. My result, 

 therefore, must be very near the truth. It is 

 not, however, quite exact. But, by means of a 

 law, which I shall explain more at length in the 

 following chapter, we have it in our power to 

 determine the specific gravity of this gas with 

 mathematical accuracy ; for, its atomic weight, 

 multiplied by 0-5555, (half the specific gravity 

 of oxygen gas,) is equal to its specific gravity. 

 Now, we have seen that the atomic weight of 

 this acid is 2-75 ; and 275 x 0-5555 = 1-5277, 

 which is the true specific gravity of this gas. My 

 estimate, deduced in the way just explained, 



