108 COMBUSTIBLE ACIDS. 



the crystals.* The carbonic acid gas evolved 

 amounted to 1 1 *8 cubic inches. Now, the weight 

 of this volume of that gas is 5i grains ; and as 

 carbonic acid is a compound of 2 oxygen + O75 

 carbon, it is evident that 5i grains contain just 

 1*5 grain of carbon. From this experiment it 

 appears, that 9 grains of oxalic acid crystals con- 

 tain 



Water ... 4-5 

 Carbon . . . 1-5 



6-0 



The remaining 3 grains wanting to complete the 

 weight is oxygen, which existed in the acid ; but 

 the 4%5 grains of water must be considered as 

 water of crystallization, as it can be driven off 

 from oxalate of lime without destroying the acid. 

 The true constituents of oxalic acid, therefore, 

 are 



Carbon . . . 1-5 

 Oxygen ... 3 



4-5 



But 1*5 is equivalent to 2 atoms of carbon, and 

 3 is equivalent to 3 atoms oxygen ; consequently, 



* In some of my experiments I obtained as much as 6 -5 grains of wa- 

 ter; but I give the average in the text. It is more difficult to determine 

 the water with rigid accuracy than the carbonic acid gas ; but I have been 

 led to fix upon 4- atoms, chiefly by the experiments detailed in a preceding 

 part of this section. 



