on Voltaic Comhiiialions and Arrangements, 289 



the 30th of an inch thick ; this is readily amalgftmated, and 

 tlie plates can be so easily renewed that it is not worth while 

 to use stouter. On the zinc side, or into the porous vessels, 

 is poured a solution of either muriatic acid diluted with from 

 2 to 2^ water, or, if the battery be intended to remain a long 

 time in action, of sulphuric acid diluted with 4 to 5 water*, 

 and on the platinum side concentrated nitro-sulphuric acid 

 (say specific gravity 1'55) formed by previous mixture of 

 equal measures of the two acids. The apparatus should be 

 provided with a cover containing lime to absorb the nitrous 

 gas. I have not given dimensions, as this is a matter of choice : 

 the proportions of the diagram are nearly correct, and taking 

 it at a scale of half an inch to an inch will be found a conve- 

 nient size, the width to be the same as the depth. 



I would now say a few words upon the theory of the bat- 

 tery, assuming as a postulate that the power of voltaic com- 

 binations is, ceteris paribus, as the I'esultant of the chemical 

 forces called into action. I cannot explain my views better 

 than by repeating a conclusion which I formerly deduced 

 from experiment (Phil. Mag., Feb. 1839): " It would seem 

 then that the best combination would be one with two metals 

 and two electrolytes, the generating metal being one which 

 has the strongest affinity for the anion of the electrolyte in 

 contact with it, while the other solution is most readily de- 

 composable by its cation, and does not cause a precipitate 

 upon which its own anion would react." 



The following then is my mode of explaining the superior 

 energy of this combination compared with those which have 

 been generally employed. In the common zinc and copper 

 battery the resulting power is as the affinity of the anion of 

 the generating electrolyte for zinc minus its affinity for copper; 

 in the common constant battery, it is as the same affinity, plus 

 that of oxygen for hydrogen, minus that of oxygen for copper ; 

 in the combination in question, the same order of positive af- 

 finities minus that of oxygen for azote f-. As nitric acid parts 

 with its oxygen more readily than sulphate of copper, resist- 

 ance is lessened, and the power correlatively increased. With 

 regard to the second material question, that of cross precipi- 

 tation : in the common combination zinc is precipitated on 



* Dr. Faraday has shown that 1'336 is the best specific gravity for sul- 

 phuric acid as an electrolyte. As however the specific gravity of the acid 

 of commerce differs much from that of pure acid, the degree of dilution 

 must depend on the acid employed. 



t I have thrown out of the case the resistance to decomposition of the 

 solution in contact with the zinc or generating electrolyte as common to 

 all the three combinations, respect being had to the other conditions ; the 

 more easy this is of electrolyzation the better. 



Phil. Mas. S. 3. Vol. 15. No. 96. Oct. 1839. U 



