1820.] Specific Graviti/ of Gases. 257 



According to Kirwan, it is 2'265 



Davy 2-1930 



These two results do not agree with each other, the one being 

 hio-lier and tire other lower than ours. We were at such great 

 pams to procure the gas perfectly pure, and the specific gravities 

 were taken with such scrupulous attention to accuracy, that I 

 am disposed to conriider our result as approaching as near accu- 

 racy as our apparatus and method of proceeding would admit; 

 near enough 1 am persuaded to enable us to determine the 

 weight of an atom of sulphur with perfect precision. 



When sulphur is burned in oxygen gas, that gas is converted 

 into sulphurous acid gas without undergoing any alteration in its 

 bulk. It follows from this, that in order to determine the pro- 

 portions of oxygen and sulphur of which this gas is composed, 

 we have only to subtract the specific gravity of oxygen gas from 

 that of sulphurous ackl gas. The remainder will "be the weight 

 of sulphur, that of the oxygen in the gas beino- denoted by its 

 specific gravity. This is the same thing as it we said that a 

 volume of sulphurous acid gas is composed of a volume of 

 oxygen gas and a volume of vapour of sulphur condensed into 

 one volume ; so that the remainder gives us in fact the specific 

 gravity of vapour of sulphur. 



Sp. gr. of sulphurous acid gas 2-22216 



oxygen gas 1-11111 



1-11105 



It appears then from our experiments that sulphurous acid gas 

 is composed of 



Oxygen Mil 11 or 1-00000 



Sulphur 1-11105 0-99995 



Now these two numbers 1 and 0-99995 differ from each other by 

 only ^.^J;-^th part — a quantity greatly within the limits of una- 

 voidable error from experiment. It is impossible to doubt that 

 in reality the two numbers are precisely equal, and that the very 

 small deficiency was owing to some small error committed in 

 taking the specific gravity. If we admit the equality of the 

 numbers, then the weight of an atom of sulphur will be a 

 multiple of that of an atom of hydrogen, as is the case with the 

 atom of oxygen, azote, chlorine, and carbon ; and the weight of 

 an atom of sulphur will be precisely double the specific gravity 

 of sulphur vapour, as we have seen to be the case with so many 

 other gaseous substances ; but if we adhere absolutely to tlie 

 result of experiments without admitting any error whatever, 

 according to the method of Berzelius ; then none of these coin- 

 cidences hold — the whole simplicity disappears — and, what is 

 most provoking, we have only to admit an error amounting to 



Vol. XVI. jN°1V. R 



