INFLUENCE OF PROPORTIONS IN ELECTROLYTES. 85 



s implicity of composition, tiiat boracic acid, ammonia, perchlorides, periodides, and 

 m any other direct compounds of elements, are indecomposable. 



698. With regard to salts and combinations of compound bodies, the same simple 

 relation does not appear to hold good. I could not decide this by bisulphates of the 

 alkalies, for as long as the second proportion of acid remained, water was retained 

 with it. The fused salt, therefore, conducted, and was decomposed ; but hydrogen 

 always appeared at the negative electrode. 



699. A biphosphate of soda was prepared by heating, and ultimately fusing, the 

 ammonia-phosphate of soda. In this case the fused bisalt conducted, and was de- 

 composed ; but a little gas appeared at the negative electrode, and though I believe 

 the salt itself was electrolyzed, I am not quite satisfied that water was entirely absent. 



700. Then a biborate of soda was prepared ; and this, I think, is an unobjection- 

 able case. The salt, when fused, conducted, and. was decomposed, and gas appeared 

 at both electrodes : even when the boracic acid was increased to three proportionals 

 the same effect took place. 



701. Hence this class of compound combinations does not seem to be subject to 

 the same simple law as the former class of binary combinations. Whether we may find 

 reason to consider them as mere solutions of the compound of single proportionals 

 in the excess of acid, is a matter which, with some apparent exceptions occurring 

 amongst tlie sulphurets, must be left for decision by future examination. 



702. In any investigation of these points, great care must be taken to exclude water ; 

 for if present, secondary effects are so frequently produced as often seemingly to indi- 

 cate an electro-decomposition of substances, when no true result of the kind has oc- 

 curred (742. &c.). 



703. It is evident that all the cases in which decomposition does not occur may de- 

 pend upon the want of conduction (6/7- 413.) ; but that does not at all lessen the in- 

 terest excited by seeing the great difference of effect due to a change, not in the nature 

 of the elements, but merely in their proportions, especially in any attempt which may 

 be made to elucidate and expound the beautiful theory put forth by Sir Humphry 

 Davy*, and illustrated by Berzelius and other eminent philosophers, that ordinaiy 

 chemical aflinity is a mere result of the electrical attractions of the particles of matter. 



^ V. On a new Measurer of Volta-electricity . 



704. I have already said, when engaged in reducing common and voltaic elec- 

 tricity to one standard of measurement (377-):> and again when introducing my theory 

 of electro-chemical decomposition (504. 505. 510.), that the chemical decomposing 

 action of a current is constant for a constant quantity of electricity, notwithstanding 

 the greatest variations in its sources, in its intensity, in the size of the electrodes 

 used, in the nature of the conductors (or non-conductors (3070) through which it is 



* Philosophical Transactions, 1807, pp. 32, 39 ; also 1826, pp. 387, 389. 



