ON THE COMBUSTION OF GASES. 85 



Substances employed. Quantities of water. 



1 Ib. of Olive oil 90 



Wax 95 



^ther 80 



Pure charcoal 78 



Alcohol 67 



' Bituminous coal 60 



Baked wood 36 



Wood with 20 per cent, water ... 27 



Turf, mean 27 



From the table of Dulong and Hess we per- 

 ceive, that during the combination of one atom 

 of oxygen with two of hydrogen and one of car- 

 bon, as in light carburetted hydrogen, about 

 three times more caloric is evolved, than by the 

 combustion of the same volume of pure hydrogen ; 

 and that one atom of carbon vapour -, as it exists in 

 carbonic oxide, gives out almost precisely the same 

 amount of heat as an equal volume of hydrogen. 

 It would also appear from the same table, that 

 during the chemical union of oxygen with the 

 above metals, and its conversion into the state of 

 solid oxides, about twice as much caloric is 

 evolved as by the same bulk of hydrogen. So 

 that if nearly the whole is afforded by the oxygen, 

 it would be about eight times less than is given 

 out by the same weight of hydrogen, corres- 

 ponding with the difference between their atomic 

 weights ; for hydrogen is sixteen times lighter 

 than oxygen : from which it would follow, that 

 during the combination of oxygen with carbon 

 and hydrogen, the atom of each gives out the 

 same quantity of heat. 



