TllANSACTIONS OF THE SECTIONS. 37 



metals of zinc and platinum, and the electrolytes concentrated nitric, 

 and diluted muriatic sulphuric acids. This little apparatus produced 

 effects of decomposition equal to the most powerful batteries of the old 

 construction. (^Comptes rendus, 15 April, and Phil. Mag., May 1839.) 

 In his endeavours to render a construction on this principle practically 

 useful, the author found it economical and advantageous to employ on 

 the platinum side a mixture of concentrated nitric and dilute sulphuric 

 acids as an electrolyte. He also recommends parallelopipedal instead 

 of cylindrical vessels. 



" The hastily-constructed battery, which accompanies the paper, con- 

 sists of an outer case of wood, height 5\ inches, breadth 5, width 3, (it 

 should be of glazed earthenware, similar to the Wollaston troughs,) 

 separated into four compartments by glass divisions ; into these com- 

 partments are placed four flat porous vessels, the interior dimensions of 

 which are 5"2^ and y^gths of an inch, the thickness of the 'parois' ^th 

 of an inch ; they contain each three measured ounces. The metals (four 

 pair) expose each a surface of 16 square inches, and the battery gives, 

 by decomposition of acidulated water, 9 cubic inches of mixed gases per 

 minute: charcoal points burn brilliantly, and it heats 6 inches of plati- 

 num wire, ^^gth of an inch diameter ; its effect upon the magnet, when 

 arranged as a single pair, is proportionately energetic ; it is constant 

 for about an hour without any fresh supply of acids. The porous 

 vessels are identical in their constitution with the common tobacco- 

 pipe. 



" As far as my experiments go, its power with reference to Mr. 

 Daniell's battery is, ' ccBteris paribus,' as 16 to 1 ; but the relative pro- 

 portions vary somewhat with the series. The cost of the whole appa- 

 ratus is £2 2s. 



" During the operation of this battery the nitric acid, by losing suc- 

 cessive portions of oxygen, assumes first a yellow, then a green, then a 

 blue colour, and, lastly, becomes perfectly aqueous ; hydrogen is now 

 evolved from the platina, the energy lowers, and the action becomes 

 inconstant. It is worthy of remark, as an argument for the secondary 

 nature of metallic precipitation by voltaic electricity, that the oxidated 

 or dissolved zinc remains entirely (or at least by far the greater por- 

 tion) on the zinc side of the diaphragm, the hydrogen alone appears to 

 be transferred ; and yet the reversal of affinities which the theory of 

 reduction by nascent hydrogen supposes, is an enigma difficult of solu- 

 tion. 



" I have invariably observed in this battery a current of endosmose 

 from the zinc to the platinum, or with the ciirrent of positive electricity. 



" The rationale of the action of this combination, according to the 

 chemical theory of galvanism, appears to be as follows : In the com- 

 mon zinc and copper combination, the resulting power is as the affi- 

 nity of the anion of the electrolyte for zinc minus its affinity for 

 copper ; in the constant battery it is as the affinity of the anion for 

 zinc, plus that of oxygen for hydrogen, minus that of oxygen for 

 copper. In the combination in question the resulting power is as 

 the affinity of the anion for zinc, plus that of oxygen for hydrogen, 



