Electrolysis of Secondary Compounds. 351 



fully neutralizing with acid or alkali, as the case might re- 

 quire, the quantity of salt decomposed was almost, if not ex- 

 actly, equivalent to the gas evolved. 



(Thus if 1 J '8 cubic inches of oxygen had been evolved from 

 the zincode, and 23'6 cubic inches of hydrogen from the 

 platinode [the results of the decomposition of 4 f 5 grains of 

 water], by neutralization it was found that the zincode cell 

 contained about 20 grains of free sulphuric acid, and the 

 platinode 16 grains of free soda, numbers which are equiva- 

 lent to the quantity of water decomposed ; meantime from 

 the single voltameter 35*4 cubic inches of mixed gases [also 

 the result of the decomposition of '5 grains of water J had 

 been collected). 



These experiments were repeated upon sulphate of potass, 

 phosphate of soda, sulphate of ammonia^ showing the analogy 

 of ammonia with metallic salts, and nitrate of potass, with 

 corresponding results. The determination of the quantity of 

 alkali in the latter instance was not possible, owing to the 

 formation of a quantity of ammonia at the platinode, from the 

 reaction of the disengaged hydrogen upon the nitric acid of 

 the salt. 



The carbonates wei'e examined in a similar manner with 

 like results. Oxalate of ammonia yielded nothing but pure 

 carbonic acid at the zincode, whilst hydrogen and ammonia 

 appeared at the platinode. The reason of this is evident from 

 the following formula: 



Oxalic acid. Carhonic acid. 



(2C + 3O) + O = 2 (C +2O) 



the equivalent of oxygen afforded by the electrolytic decom- 

 position of the salt being just sufficient to convert one equiva- 

 lent of oxalic acid into two equivalents of carbonic acid. 



Sulphovinate of potassa was decomposed also in equivalent 

 proportions,the acid and oxygen passing to the zincode whence 

 the gas escaped uncombined hydrogen and potassa being as 

 usual developed at the platinoae. From the preceding ex- 

 periments it appears, " that in the electrolysis of a solution 

 of a neutral salt in water a current which is just sufficient to 

 separate single equivalents of oxygen and hydrogen from a 

 mixture of sulphuric acid and water, will separate single equi- 

 valents of oxygen and hydrogen from the saline solution, while 

 single equivalents of acid and alkali will make their appear- 

 ance at the same time at the respective electrodes." 



These relations were found equally to hold good, whether 

 the oxygen was allowed to escape from the zincode of the 

 double diaphragm cell, or whether it was absorbed by an 



