MERCURIC SALTS CHANGE INTO EACH OTHER. 1 75 



Evidently, therefore, aerial oxidation plays no sensible part in the 

 conversion of mercurous nitrate to mercuric nitrate. 



Oxygen would seem, indeed, to impede the conversion in the 

 absence of basic salt, but not in its presence. For, at the end of 19 

 days, the conversion to mercuric salt was half as great again in a 

 closed flask in which the air had been replaced by carbon dioxide as 

 it was in a closed flask containing air. 



On the other hand, in a flask at the end of 19 days, in which 2 

 grams mercurous nitrate had been put with lOcc. water in an atmo- 

 sphere of oxygen itself, there was found just the same quantity of mer- 

 curic radical as in the flask holding carbon dioxide. Also in 33 

 days two flasks, one of which had enclosed carbon dioxide, and the 

 other air, showed the same contents of mercuric radical, a result, 

 which, I consider, is brought into conformity with that obtained in a 

 similar pair of flasks opened in 19 days, by allowing for the consump- 

 tion of nitric acid, which had taken place, counteracting the impeding 

 action of the oxygen. For, the conversion by light being one in 

 which nitrous acid is formed from the nitric acid, oxygen will oxidise 

 this to nitric acid in acid solution, while it will not oxidise the mer- 

 curous nitrite existing as such in the comparative absence of nitric 

 acid. 



In these experiments, comparison was also made as to the 

 influence of mercury vapour, which Barfoed has shown to be such a 

 material presence in any atmosphere in contact with mercury. Some 

 -of the flasks employed had each a bent tube of good diameter passing 

 through the cork and at its outer end dipping in a vessel of mercury 

 throughout the experiment. The effect was striking where the ex- 

 periment lasted for 33 days. Whether the atmosphere was air or 

 carbon dioxide, the production of mercuric radical was only two-thirds 

 in a mercurial atmosphere of what it was in a non-mercurial atmo- 



