RICHARDS AND STULL. — FARADAY's LAW. 411 



diately for the electrolysis, being maintained at the high temperature 

 with the help of a suitably arranged alcohol lamp. Great care was 

 exercised to prevent the possibility of electrical leakage, the connections 

 being made by carefully insulated air lines. 



When a first crude experiment had shown the feasibility of the 

 arrangement, three more careful preliminary experiments were made. 

 After the completion of each allotted time, the current of 0.2 ampere 

 was broken, the two porous cups removed, and the two electrolytes 

 decanted. Each cathode-crucible was thoroughly I'insed and allowed to 

 stand for fifteen to eighteen hours in water. Two more washings with 

 water, two with alcohol, and a thorough drying at 160° C. completed 

 the treatment. In those cases when a trace of metallic silver was found 

 in the decanted liquid, this trace was carefully collected on a Gooch 

 crucible, thoroughly washed, and weighed. It was noted that the upper- 

 most crystals deposited at the higher temperature were somewhat larger 

 than the others, and also that no "anode dust" formed at 250°. The 

 first of these facts may be ascribed to local action, due to slight thermal 

 inconstancy* while the second is probably due to the rapid adjustment 

 of equilibrium at the high temperature. Thus the chemical explanation 

 given by Richards and Heimrod f of the appearance of the " anode dust" 

 in aqueous solutions is supported ; for if the anode dust were due solely 

 to the mechanical detaching of bits of silver, there is no obvious reason 

 why this process should not occur at high temperatures as well as at low 

 temperatures. 



Since all crystals formed from solutions contain included mother 

 liquor, concealed in inaccessible cells, t the silver which had been de- 

 posited from the molten solution was now examined for included sodic 

 and potassic nitrates by dissolving it in pure nitric acid, precipitating 

 the silver by hj'dric sulphide, evaporating the filtrate, dissolving and 

 filtering the residue, drying once more, and finally weighing. Hydric 

 sulphide was used in order that platinum vessels might be employed 

 throughout. The mother liquor included in tlie crystals deposited from 

 aqueous solution was assumed to be 0.016 per cent, the average of many 

 determinations. § 



* Gladstone and Tribe (Phil. Mag.), (5) 11, 508. 

 t These Proceedings, 37, 428 (1902). 



J The effect of sucli inclusion is particularly obvious in tlie work of ^lerrill 

 already quoted. 



§ liichards and Heimrod, These Proceedings, 37, 441. 



