286 Dr. Murray on the Chemical Constitution of [Oct. 



infer the existence of a relation in proportion of sulphur to oxygen 

 intermediate between that of sulphurous and sulphuric acid ; a 

 similar relation may exist in the case of carbon, intermediate 

 between carbonic oxide and carbonic acid ; and with the addi- 

 tion of hydrogen, may give rise to acidity. Lastly, there is 

 some reason also to suppose the existence of a combination of 

 sulphur with oxygen in a lower proportion than that in sulphurous 

 acid. There may be a similar combination with carbon, which 

 may also, with an additional proportion of hydrogen, produce 

 acidity. It remains to inquire how far the composition of any 

 of the vegetable acids can be brought under these laws. 



Carbonic acid is the binary compound of carbon and oxygen. 

 With the addition of hydrogen there is every reason to infer, 

 that, as in the case of all the other binary acids containing 

 oxygen, an acid will be formed of increased power. Oxalic acid 

 is the strongest of the vegetable acids ; and the results of its 

 analysis will be found to lead to the conclusion that it is this 

 ternary compound. 



Berzelius submitted oxalic acid to experiment by combining 

 it with oxide of lead, drying the oxalate, and decomposing it by 

 heat. His object in following this method was to abstract the 

 combined water of the acid, and to operate upon it in what is 

 considered as its real state. He accordingly found, that the acid 

 loses water in entering into this combination ; and he objects to 

 a preceding analysis by Gay-Lussac, in which the oxalic 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 

 retained. 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 analysis as it exists in a dry 

 oxalate, exactly as that of sulphuric acid is inferred from its 

 analysis in the state in which it exists in a dry sulphate. The 

 reasoning of Berzelius, therefore, was relatively just; and on 

 these data his results, though they have been objected to, as 

 they involve difficulties in the atomic hypothesis, are correct. 

 But in conformity to the doctrine I have illustrated, it is evident 

 that the composition of the acid is not thus obtained, and that 

 what exists in a dry oxalate, such as oxalate of lead, is a differ- 

 ent combination. The crystallized oxalic acid is what ought to 

 be submitted to analysis if it contained no water of crystalliza- 

 tion ; 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 oxalate of lime ; and hence the 

 results given by Gay-Lussac (if experimentally correct, and they 

 appear to be singularly so) give its real composition. They are 



