DR. J. P. JOULE ON SOME AMALGAMS. 115 



X. — On some Amalgams. 

 By J. P. Joule, LL.D., F.E.S. &c. 



E.ead January yth, 1862. 



The experiments I am about to describe were made twelve 

 years ago, but their publication was delayed to tbe present 

 time in the hope of being able to extend them. Although 

 I have not found an opportunity of doing so, I trust that 

 these comparatively old observations vrill be deemed of 

 sufficient interest to justify me in having submitted them 

 to the Society. 



My attention was first directed to the subject through 

 my wish to discover a ready means of procuring a per- 

 fectly true and polished metallic surface. Since it was 

 believed that mercury refused to enter into combination 

 with iron, I thought that by depositing the latter on 

 raercury, a plate of it would be formed possessing a smooth- 

 ness equal to that of the fluid metal. However, on making 

 the experiment, I found that the iron entered into com^ 

 bination with the mercury, forming an amalgam ■^. 



One element of a DanielPs battery was amply sufficient 

 for the purpose. Its zinc plate was connected by a wire 

 with a globule of mercury covered by a solution of sul- 

 phate of iron, whilst an iron wire attached to its copper 

 plate, and dipping into the solution, completed the circuit. 

 The iron wire gradually dissolved, whilst an equal portion 

 was taken up by the mercury, which, in doing so, by de- 



'^ In consequence of iron possessing nearly the same affinity as hydrogen 

 for oxygen, there is considerable difficulty in depositing it electrogchemically 

 on a metallic plate. I have only once or twice obtained a good electrotype 

 deposit on a polished surface, to which the iron adhered so firmly that it 

 could only be remoTed by abrasion. Even in the process of amalgamating 

 iron, the constant evolution of hydrogen from the mercury shows that de- 

 composition of water takes place simultaneously with that of the salt of 

 iron. 



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