Acids, Alkalis, and their Compounds. 95 



loses water in entering into this combination ; and he objects 

 to a preceding analysis by Gay-Lussac, in which the oxaHc acid 

 had been operated on in the state of oxalate of lime, as in this 

 combination the water of composition is not abstracted. His 

 objection is valid, on the doctrine which has been universally 

 adopted by chemists, of acids containing water essential to their 

 constitution, which is abstracted when they enter into combina- 

 tion with a base, such as oxide of lead, in which water is not re- 

 tained. And if oxalic acid in passing into this combination lose 

 water, as is the case, then on this idea its constitution ought to 

 be determined from its analvsis as it exists in a drv oxalate, ex- 

 actly as that of sulphuric acid is inferred from its analysis in the 

 state in which it exists in a dry sulphate. The reasoning of Ber- 

 zelius, therefore, was relatively just ; and on these data his re- 

 sults, though thev have been objected to, as they involve diffi- 

 culties in the atomic hvpothesis, are correct. But in conformity 

 to the doctrine I have illustrated, it is evident that the composi- 

 tion of the acid is not tlius obtained, and that what exists in a dry 

 oxalate, such as oxalate of lead, is a different combination. The 

 crystallized oxalic acid is what ought to be submitted to analysis 

 if it contained no water of crystallization ; but as it does contain a 

 portion, this is to be removed, without abstracting what has been 

 called water essential to the acid. It exists in this state in ox- 

 alate of lime ; and hence the results given by Gay-Lussac (if ex- 

 perimentally correct, and they appear to be singularly so) give its 

 real composition. They are accordingly strictly conformable to 

 the view I have stated of the composition of this acid. The pro- 

 portions he assigns are 26"56 of carbon, 70'(i9 of oxygen, and 

 2*7.T of hydrogen*. Now carbonic acid is composed of 27*4 of 

 carbon, and 726 of oxvgcn. The proportion of carbon and oxy- 

 gen, therefore, in oxalic acid, is precisely the same ; and the sole 

 difference in composition from carbonic acid is in the proportion 

 of hydrogen it contains. 



The constitution of oxalic acid may likewise be inferred indi- 

 rect! v from the method of Berzelius: and it will be satisfactory 

 if a coincidence is thus obtained. The composition of the real 

 acid, as it is called, existing in oxalate of lead, is stated by Ber- 

 zelius at ;i3'22 of carbon, (iG"53 of oxygen, and 02.5 of hydro- 

 gen. But to this, to express the true composition of the acid, 

 are to be added the proportions of oxygen and hydrogen expended 

 in the formation of water, in the nuitual action of the acid and 

 the oxide of lead. The quantity of hydrogen is inferred frtun the 

 (juantity of oxygen : and there are different principles connected 



• Ileclicrc/ics I'/ii/sico-Cliimiijiicf, tonic ij. j). .'502. 



with 



