246 Dr. TJtoinsoji on lite Oct. 



ness of our carbonic acid gas, we found that when 200 volumes 

 of it were absorbed by water, one volume of unabsorbable gas 

 lemained. But this i)roportion I believe to be excessive ; 

 "because when water is saturated with carbonic acid gas, the 

 whole of the common air which it previously contained is driven 

 off; so that part of this residue was actually separated from the 

 water. I am disposed to think that the carbonic acid gas 

 which we experimented on was composed of a mixture of 505^ 

 volumes of pure carbonic acid and one volume of air ; or 

 that it contained nearly 3— th part of its volume of common air. 

 If this opinion be well founded, the true specific gravity of car- 

 bonic acid gas is 1"5277. The result which we obtained is only 

 - ^^ ^ th part less than this number — a result which is certainly 

 far within the limits of unavoidable error from the experiment- 

 I shall now state the reasons why I consider 1-5277 as the true 

 specific gravity of carbonic acid gas. 



It has been demonstrated that carbonic acid gas is a com- 

 pound of carbon and oxygen, and that when oxygen gas is 

 converted into carbonic acid gas, its volume is not altered. 

 Therefore to ascertain the weight of carbon which a given volume 

 of carbonic acid gas contains, we have only to subtract the 

 specific gravity of oxygen gas from that of carbonic acid gas, 



the remainder represents the weight of carbon united with I'llll 

 of oxygen. 



Specific gravity of carbonic acid gas. l-o277 

 Specific gravity of oxygen gas I'llll 



Carbon = 0-416()' 



The number 0'4166 must represent the specific gravity of a 

 volume of carbon, supposing it in the gaseous state, and carbonic 

 acid gas must be considered as a compound of one volume 

 oxygen gas and one volume of carbon condensed into one 

 volume, or of two atoms of oxygen and one atom of carbon. 



If we represent the specific gravity of oxygen by unity, then 

 the specific gravity of carbon will become 0-375 ; for it is 

 obvious that 1-1111 : 1 :: 0-4166 : 0-375; but 0-375 x 2 = 

 0*75. I\o\v 0-75 represents the weight of an atom of carbon — 

 certainly very nearly — I am of opinion accurately. 



Carbon agrees with hydrogen, azote, and chlorine, in the 

 respect that the weight of its atom is just double that of its spe- 

 cific gravity, reckoning the specific gravity of oxygen unity. 

 We have found that the weights of the atoms of oxygen, azote, 

 and chlorine, are multiples of the weight of the atom of hydro- 

 gen ; for the weight of the atom of hydrogen is 0-125, and 



0*125 X 8 = 1-00 = atom of oxygen 

 0-125 X 14 = 1-75 = atom of azote 



