M. Viard on the Electro-chemical Deportment of Oxygen. 247 



Many other series were obtained, but as they presented exactly 

 the same form as the above, the latter may suffice ; the following 

 table merely indicates the several experiments made : — 



The experiments with zinc were made either with distilled 

 zinc or with amalgamated zinc. 



For some time the experiments with iron failed; for when 

 ordinary iron wire, cleaned with emery paper, was used, the needle 

 often made sudden leaps, thus rendering the observations ex- 

 tremely irregular. It was only by employing perfectly polished 

 steel knitting needles that regular results could be obtained. 



Sometimes copper wires were used, but oftener, plates of copper 

 beaten flat with the hammer. 



The silver plates had been reduced from chloride of silver by 

 means of potash, and may be regarded as very pure. The cop- 

 per as well as the silver plates were well cleaned with emery 

 paper. 



The above tables show clearly the deportment of oxygen ; for 

 example, from the results obtained with zinc and water, we see 

 that when the wires were plunged into boiled water, the devia- 

 tions were almost null ; that when the boiled water on the right 

 was replaced by aerated water, the deviation announced that the 

 right wire had become negative; and that when the aerated 

 water was to the left, the direction of the deviation was changed. 



When the two wires were plunged into aerated water, the 

 deviation was again almost null ; but when the aerated water on 

 the right or on the left was replaced by boiled water, the right 

 or left plate became positive. 



The other tables but extend the same results to other metals 

 and other electrolytes. 



Instead of operating as above explained, another method was 

 often employed, which, though perhaps less sure, yet when em- 

 ployed with care, leaves no doubt as to the # influence of oxygen. 



Two plates, as identical as possible, were covered with test- 

 tubes (fig. 3) ; these test-tubes and the vessel which served as 

 their recipient were filled with the same electrolyte, and subse- 

 quently oxygen was passed into the one tube and the current 

 observed. The results of these experiments confirmed those 

 already given, but, I must repeat, they require gnat care in 



