CARBURETTED HYDROGEN GASES. 399 



REMARK. Frequently the oxide of carbon is produced at the 

 same time with carbonic acid. The pale blue flame which arises 

 from burning charcoal, especially when the fire is nearly burnt out, ap- 

 pears to be produced from the ignition of the nascent oxide of car- 

 bon. As fast as this gas is formed, it takes fire and burns away, 

 being converted into carbonic acid gas. Oxide of carbon appears 

 to be formed in those combustions of carbon, where the oxygen 

 is supplied slowly and with difficulty ; carbonic acid gas, where it is 

 supplied rapidly and in large quantities. Hence, when we heat the 

 oxides of mercury with charcoal, we obtain carbonic acid ; when the 

 oxides of iron, we evolve oxide of carbon. 



We have every reason to believe that oxide of carbon is one of the 

 gases produced during animal and vegetable decomposition, and as it 

 is highly noxious, it may contribute to their injurious effects. 



It is observed, that as oxygen } by combining with carbon to form 

 carbonic acid, becomes heavier, we might naturally expect that car- 

 bonic oxide, containing twice as much carbon, should be heavier 

 still ; but this does not follow. Carbonic acid is heavier than oxy- 

 gen, by precisely the additional weight of the carbon, because this 

 last has assumed the aeriform condition, within the same volume as 

 the oxygen. The sp. gr. of carbonic acid being 1.527, if we deduct 

 that of the oxygen, 1.111, we have .416 for the sp. gr. of aeriform 

 carbon in the gas, and as this is combined with only half a volume of 

 oxygen, which is expressed by .555 this added to the weight of 

 the carbon =.97 If for the gravity of the carbonic oxide, which is to be 

 regarded, therefore, not as a mere solution of carbon in oxygen, but 

 as a combination of fieriform carbon with oxygen gas. 



CARBURETTED HYDROGEN GASES. 



1. HISTORY. Some of these gases must have been for a long 

 time, more or less known to mankind; as their occurrence is fre- 

 quent in the mud of marshes, in coal mines, in the matter emitted 

 from burning combustibles, and from the ultimate results of animal 

 digestion, &ic. 



But we owe the accurate knowledge of them to a few modern 

 philosophers, among whom Mr. Dalton, Dr. Henry, and Dr. Thom- 

 son, are conspicuous.* 



2. GENERAL VIEW. It seems, at first, as if there must an immense 

 number of carburetted hydrogen gases ; since we can scarcely ope- 

 rate by destructive processes, upon any animal or vegetable matter 



* The following statements of facts are drawn principally from the writings of 

 Dr. Henry and Dr. Thomson. 



I .972 is the number we have hefore stated. 



