OXALIC ACID. 107 



Thus, the quantity of hydrogen found by every 

 succeeding experimenter was less than that found 

 by his predecessor. The reason was, that he 

 was at more pains to free the salt operated upon 

 from moisture. 



We have no certainty that Berzelius' salt was 

 perfectly anhydrous it might, and probably did, 

 retain a little water. It occurred to me, that the 

 question of the existence of hydrogen in oxalic 

 acid would be best determined by employing the 

 crystals, which are now known to contain exactly 

 half their weight of water. Nine grains of the crys- 

 tals were triturated with 200 grains of peroxide 

 of copper, and exposed to a low red heat in a cop- 

 per tube : to the mouth of this tube was ground a 

 glass tube, filled with fused chloride of calcium, 

 in very small fragments ; the extremity of this 

 tube was plunged into the mercurial trough, and 

 the gaseous products were collected in graduated 

 glass jars. By this process, which was originally 

 suggested by Gay-Lussac, the whole of the acid 

 was resolved into carbonic acid gas and water 

 the water was absorbed by the chloride of calci- 

 um, while the carbonic acid gas was collected 

 over mercury. Making allowance for the small 

 quantity of hygrometrical water which peroxide 

 of copper always contains, as was shown by Ber- 

 zelius, Saussure, and Mr. Walter Crum, the 

 weight of the water retained by the chloride was 

 very nearly i*5 grains, or just half the weight of 



