210 Dr. Macneven's Exposition of [Sept. 



the theory of atoms represents in a solid form, I prefer the 

 theory of atoms as subject, on the whole, to fewer difficulties. 

 38" Oxygen, 1. 



39. It was proved in sections 7, 8, 9, that hydrogen is but 

 one-eighth parts as heavy as oxygen. Hence, by dividing 8 

 into 1 we obtain the fractional proportion for hydrogen 0-125. 



40. Carbon. — When carbon is burned in oxygen, the volume 

 of the gas is not altered, but it is converted into carbonic acid 

 o-as. Hence, if from the weight of 100 cubic inches of carbonic 

 acid o-as = 46-313 grs. we subtract the weight of 100 cubic 

 inches of oxygen gas = 33-688, the difference 12-641 grs. gives 

 the weight of carbon in 100 cubic inches of carbonic acid gas. 

 It shows that this gas is composed, per cent, of 27-29 parts 

 carbon and 72-71 oxygen, for 46-313 carbonic acid is to 12-641, 

 its proportion of carbon, as 100 carbonic acid is to 27-29, its 

 proportion of carbon ; and by subtracting the carbon, the 

 remainder 72-71 gives the oxygen. 



There is also another combination of oxygen and carbon 

 necessary to be considered before we can determine the propor- 

 tional number for carbon. It is carbonous oxide, a gas that may 

 be formed by partially decomposing carbonic acid. 



When a well dried carbonate, such as carbonate of barytes, or 

 lime, is distilledwith dry iron filings, the iron attracts apart of 

 the oxygen of the carbonic acid of the carbonate, and the 

 remainder, minus the portion of oxygen thus taken from it 

 becomes carbonous oxide ; a gas containing less oxygen, there- 

 fore, than carbonic gas. But if to the same carbonous oxide 

 half its volume of pure oxygen gas be now added, and the elec- 

 tric spark be passed, it becomes carbonic acid gas again. In 

 these two experiments the carbon has not been affected ; it is 

 the saiTie in both, the oxygen only has been partially taken off 

 in the first, it is restored in the second. Now, since there is the 

 same weight of carbon = r2'641 grains in 100 cubic inches of 

 both, deducting this from the weight of both, we get the weight 

 of oxygen in each. 



Thus *46-313 - 12-641 = 33-688 the oxygen in 100 carbo- 

 nic acid; and f 29-158 - 12-641 = 16-517 the oxygen in 100 

 carbonous oxide. But as 16-517 is very little more than half 

 33-688, it is proved that carbonous oxide contains but half the 

 oxyo-en of carbonic gas, and, therefore, that there are twice as 

 many atoms in the latter as in the former ; and that if the first 

 be abinary compound consisting of an atom carbon and an atom 

 oxygen, the second is a ternary compound of an atom carbon and 

 two atoms oxygen. 



To find the proportional weight of the atom of carbon take 

 the oxide of carbon which is binary, and as 16-517 weight of 



» Weiglit of ICO cubic inches carbonic gas. 



t Weight of 100 cubic inches carbonous oxide gas. 



