172 Drs. A. Matthiessen and C. Vogt on the Influence of 



a decrement of the conducting power, has induced us to make 

 the following experiments. 



The mercury employed was purified by allowing it to stand 

 for a length of time under a solution of protonitrate of mercury, 

 and before use heating it on a water-bath for about half an hour 

 with dilute nitric acid, washing with distilled water, and drying 

 on the water-bath. 



Before commencing the experiments, it was necessary to test 

 whether the assertion made by Siemens*, "that not only docs 

 the absorbed oxygen, but also all metallic impurities increase the 

 conducting power of mercury," is correct. Is oxygen really 

 absorbed by mercury ? This question may be answered by 

 the following experiments : — ■ 



I. Mercury which had been treated with dilute nitric acid on 

 a water-bath was well washed with distilled w r ater (previously 

 boiled to expel the air) and carefully dried with bibulous paper ; 

 a part of it was heated on the water-bath for half an hour, being 

 well stirred during that time, and part dried in a Liebig's 

 drying tube at 100° C. in a current of dry and pure hydrogen. 

 These specimens did not show the slightest difference in their 

 conducting power. 



II. Another portion, after being dried in the water-bath, was 

 shaken with oxygen in a bottle at the ordinary temperature for 

 twenty minutes, and allowed to stand for three hours, during 

 which time it was repeatedly shaken up. This also had the 

 same conducting power as the above. 



III. Another portion of the same mercury was boiled in an 

 evaporating dish in contact with air for a quarter of an hour, to 

 allow the formation of suboxide. This also showed no altera- 

 tion in the conducting power. It may be mentioned that the 

 apparatus we employed for the determination of the resistances 

 will distinctly show 0*01 per cent, difference in the resistance. 



IV. If mercury absorbed oxygen, it is probable that it would 

 give it out again on solidification, as in the case of silver. 

 Rose, however, states in his paper " On the Spitting of Silver -j-/' 

 that he had often frozen large quantities of mercury, but never 

 observed the phenomena which occur with the spitting of silver. 



From the foregoing it would appear that mercury does not 

 absorb oxygen or oxide; or if it does, only to so small an 

 extent that its conducting power is not altered by it. Now, as 

 we shall prove that a veiy minute quantity of foreign metal 

 materially affects the conducting power of mercury, we think 

 we are justified in stating that pure mercury will neither absorb 

 oxygen nor dissolve either of the oxides of mercury. That the 



* Phil. Mag. January 1861. 



f Poggendorff's Annalen, vol. lxviii. p. 290. 



