430 Mr. W. R. Grove o?z a ncna Voltaic Combination. 



netism, retention, discharge, and some other points, with an 

 application of the theory to these effects, and an examination 

 of it by them. 



Royal Institution, Nov. 16, 1837. 



J' 3 



Fig. 11. 



Omitted in page 365. (1246.) 



By W. R. Grove, 



LVI. On a new Voltaic Combination. 

 Esq., M.A. 



To the Editors of the Philosophical Magazine andjournal. 

 Gentlemen, 

 f\^ first hearing of porous porcelain being employed as a 

 ^^ diaphragm for preventing the mutual precipitation of the 

 metals on each other in voltaic combinations, it struck me 

 that one of the plates of metals usually employed might be 

 dispensed with by precipitation upon the other from a metal- 

 lic solution. After some unsuccessful trials, I constructed a 

 trough as following: a piece of common stout millboard of 

 the length required, and of breadth sufficient to form the bot- 

 tom and sides, is separated lengthwise into three parallel divi- 

 sions by cuts one-third through ; it is then covered with a thin 

 layer of cement and bent up into the form of a trough ; four- 

 inch squares of common sheet iron and unglazed porcelain 

 plates of the same dimensions are then warmed and slid alter- 

 nately into the trough, as in Cruickshank's form, at about three 

 tenths inch distance *. A solution of sulphate of copper and 

 dilute acid being poured into the alternate cells, a very active 

 series is formed by the precipitation of the copper on one sur- 



* Pasteboard is preferable to wood for the formation of these troughs : it 

 has not strength sufficient by its warping to crack the cement, is much 

 more easily constructed, and a better insulator; it should be thinly coated 

 with varnish on the outside to prevent capillary absorption by accidentally 

 touching liquids. The plates of porous ware here mentioned may be con- 

 veniently employed for rendering constant the common Cruickshank 

 trough, being warmed sufficiently to melt the cement and slid into the 

 cells. 



