Electrolysis of Secondary Compounds. 181 



firmed by their repetition, that the three hydrates of the phos- 

 phoric acid constitute three essentially distinct acids, which 

 may be expressed as follows : — 



H + Pg Og proto-hydrate, 

 Hg + Pg O7 deuto-hydrate, 

 Hg + Pg Og trito-hydrate, 

 and that when disengaged from their corresponding saline 

 compounds by the power of the voltaic current, they travel as 

 three distinct oxyphosphio7is in the circuit. This view, which 

 cannot be doubted as arising from the properties of the acids 

 so disengaged, derives confirmation from the observation that 

 the quantity of acid transferred from the monobasic phosphate 

 of soda was so much greater for the same amount of hydrogen 

 disengaged, than from the dibasic and tribasic salts of the 

 same base. 



We had thus the gratification of establishing by independ- 

 ent testimony the correctness of Prof. Graham's theory of the 

 phosphates, and it is with pleasure we also observe that his 

 view of the basic character of water in certain saline com- 

 pounds* is confirmed by the results of the electrolysis of the 

 three tribasic phosphates ; from all of which the same acid 

 was separated, notwithstanding that in two instances water 

 obviously constituted one of the three equivalents of base. In 

 our corresponding view, one of the three equivalents of metals 

 was represented by hydrogen. 



3. Next in natural order seems to stand the inquiry whether 

 the salts of other tribasic acids would afford analogous results 

 to those of the tribasic phosphates. 



{/.) For this purpose we selected the tribasic arseniate of 

 potassa and water (KO, 2HO, Asa O5) (binarseniate), the pla- 

 tinode cell was charged with a solution of the salt, and the 

 zincode cell and connecting cell with solution of potassa. The 

 combination was found to conduct very well, and oxygen and 

 hydrogen were given off at their respective electrodes. The 

 solution in the platinode cell assumed a grayish appearance, 

 but there was no smell of arseniuretted hydrogen, nor was any 

 arsenic deposited upon the electrode. The solution had be- 

 come neutral to test paper. The liquid in the zincode cell 

 was carefully neutralized by acetic acid, and afterwards pro- 

 duced in solution of nitrate of sliver, the characteristic brick- 

 red precipitate of the arseniate of silver (3AgO, AsgOg), so 

 that there could be no doubt that the tritoxarsenion had tra- 

 velled into the zincode cell. 



The complicated secondary actions which take place in the 



r* A paper on this subject by Prof. Graham will be found in Phil. Mag. 

 S. 3. vol. vi. p. 327.— Edit.] 



