1320.] Specific Gravity of Gases. 249 



We see from this that the true specific gravity of this gas when 

 in a state of purity is 0-9722. The result which we obtamed is 

 less than the truth by ,x.th i^art. Th.s is a greater error than 

 .ve could have committed if oar gas had been free from impurity 

 But if we suppose the gas upon which we tried our experiments 

 to have been a mixture of 171 volumes of pure carbomc oxide 

 gas and 1 volume of carburetted hydrogen gas, such a mixture 

 would have the very specific gravity which we found. ISow 

 thouoh 1 have prepared carbonic oxide gas by heating i on 

 filino^s and chalk more than 40 times, 1 have never obtained it 

 more free from carburetted hydrogen gas than the specimen 

 employed for ascertaining Its specihc gravity. , . ., . 



1 consider it then as demonstrated, that carbdmc oxide and 

 carbonic acid gases are composed as follows : 



Carbonic oxide ofhalf volume of oxygen gas = 0-5555 

 one volume carbon = 0-4166 



= 0-9722 

 So that the diminution of volume is one-third. 



Carbonic acid of 1 volume oxygen = Mill 

 1 volume carbon 0-4166 



1-5277 

 So that the diminution of volume is one-half. 



Or substituting atoms for volumes, carbonic oxide is a com- 

 pound of _ , „|^ 

 1 atom oxygen - ^'J^;! 



1 atom carbon — v /o 



Atom of carbonic oxide = 1"'-* 



Carbonic acid is a compound of 



2 atoms oxygen = ■^'^^ 



1 atom carbon ~ ^'^'^ 



Atom of carbonic acid = ~' '-^ 



So that in both of these gases the weight of the atom is double 

 the specific gravity, reckoning the specific gravity ot oxygen 

 vinity ; for in'that case we have the specific gravities ot these 

 gases as follows : 



Carbonic oxide 0-S75 and 0-875 x 2 = 1*75 

 Carbonic acid 1-375 and 1-375 x 2 = 2-75 



Thus these two gases exactly agree with hydrogen, azote, 

 chlorine, steam, and protoxide of azote. 



3. 0/eJia,it G«.s.— Olefiant gas is obtained by mixing together 



