593 Mr, J. Brown on Removal of the Voltaic 



themselves, a voltaic cell is produced of which the films are 

 the electrolyte. 



In 1888 I trie*] the effect of freezing the films 0:1 a Volta 

 condenser by subjecting it to a temperature of —21° C. as 

 obtained bja mixture of ice and common salt, with indefinite 

 results, owing perhaps to unsuitable apparatus. 



In 1900 Majorana * published experiments showing that 

 on cooling a zinc | gold couple to the temperature of liquid 

 air. the volta effect was reduced from '8b volt to *05 volt. 

 and rose again on the return to ordinary temperature to 

 •75 volt. With couples of other metals similar results were 

 obtained. This effect, in my opinion, corresponds with the 

 cessation of chemical activity at the temperature employed. 



To get rid of chemical action at the surfaces of the metals 

 by the removal of the chemically acting substance, many 

 attempts have been made, chiefly by inclosing the couple in 

 a vessel exhausted to a. high degree or surrounding it with 

 "pure" inert gases, but without success. Heating the 

 metals has also been frequently tried, but the oxidation or 

 other alteration of their surfaces at higher temperatures 

 intervenes, precluding any true estimation of the effect 

 sought to be investigated. 



In order to avoid this source of error in the experiments 

 now to be described. 1 immersed the couple in a bath of oil 

 of high boiling-point. 



The diagram represents in section a zinc-copper Yolta 

 condenser with plates C, Z 11*4 centimetres in diameter, 

 screwed on the ends of iron rods A and B of which the lower 

 is fixed and the upper slides in an insulated guide-tube. 

 Means are provided for setting the plates parallel and at a 

 minute distance apart. D represents an enamelled iron dish, 

 a hole in the bottom of which provides for its being fixed 

 between the zinc and the collar i on rod B so as to hold the 

 oil. 



Heavy petroleum known as Price's gas-engine oil was 

 used. Owing to its viscosity the plates (having nearly true 

 surfaces) could be only slowly separated, although radial 

 grooves were cut in the zinc to permit the more easy pene- 

 tration of the oil between the plates when these were being 

 pulled apart. 



The following is the order of experiment : — The plate-, 

 having been well cleaned with fine glass-paper, were set close 

 together and connected one to each pair of quadrants of the 

 electrometer. After momentarily connectino- them together 

 by a wire and then separating them in the usual way, in air. 

 * Aeead. Lined Atti, Aug. 19th ; Sept. 2nd and 16th (1900). 



