CARBON. 135 



furnish us with the requisite data for determin- 

 ing the exact composition of carbonic acid gas. 



We have three sets of experiments on the spe- 

 cific gravity of carbonic acid gas, which appear 

 to have been made with great care. The follow- 

 ing are the results obtained : 



8P. GR. OP CARBONIC ACID GAS. 



1-5196 . by Biot and Arago. 



1 '52673 . by my experiments. 

 1-5240 . by Berzelius and Dulong. ' 



These results differ too much from each other 

 to enable us to deduce from them the composi- 

 tion of carbonic acid, with the requisite degree 

 of precision \ nor have we any criterion by which 

 we can discover which of the three results is 

 nearest the truth. My own determination is the 

 highest, and that of Biot and Arago the lowest. 

 Now, if any error resulted from the impurity of 

 the gas weighed, the probability is, that it would 

 diminish the specific gravity somewhat ; for, 

 common air, the only gas likely to contaminate 

 the carbonic acid gas examined, is a good deal 

 lighter. So far the probability of accuracy ra- 

 ther inclines to my own result ; but it is not 

 sufficient to enable us to decide the point, far less 

 to determine whether my own result be not in 

 reality a little too low. This uncertainty suggest- 

 ed to me a method similar to that by which the 

 specific gravities of oxygen and hydrogen gases 



14 



