240 



12. I have endeavoured to obtain the movements without the 

 presence of an electrolyte, by passing an electric current through a 

 small globule of zinc fused upon the surface of bismuth, but the 

 ready mingling of the melted metals, and their rapid oxidation, pre- 

 vented a reliable experiment being made. 



13. It has already been shown, in the instances of fused salts upon 

 melted metals (10), that the presence of water is not a necessary 

 condition of the phenomena. 



14. The power of producing the movements is a general property 

 of electrolytes as well as of liquid metals ; I have experimentally 

 found it in the following classes of substances : organic and in- 

 organic acids ; water ; aqueous solutions of caustic alkalies* ; alkaline 

 carbonates, bicarbonates, borates, hypophosphites, phosphates, sul- 

 phides, hyposulphites, sulphites, sulphates, bisulphates, iodides, bro- 

 mides, chlorides, chlorates, nitrates, and silicates ; salts of alkaline 

 earths and of alumina ; salts of tungsten, molybdenum, chromium, 

 uranium, manganese, arsenic, and of the malleable heavy metals ; also 

 with fused salts, aqueous solutions of organic salts, and solutions of 

 salts in alcohol. The salts of tungsten, molybdenum, chromium, 

 uranium, and manganese, generally gave the weakest and most 

 variable results ; whilst sulphuric acid and solutions of alkaline 

 cyanides yielded very strong and definite movements. In feeble 

 cases of motion the globule of mercury should be placed in a narrow 

 porcelain boat, and a strong solution of the substance added until 

 the metal is only covered at its sides with the liquid ; and for still 

 greater sensitiveness, the experiment of placing a drop of the liquid 

 upon the surface of the mercury should be adopted. 



15. The mass or body of the liquid is not essential to the move- 

 ments ; mere films of solution adhering to the under surface of a 

 circular disc of brass, brought into contact with mercury under the 

 influence of a voltaic current, exhibited the phenomenon readily. 



16. To ascertain whether the current of electricity must pass from 

 the electrolyte into the metal, or vice versa : 1st. A layer of mercury 

 was placed in a narrow glass beaker, upon it a shallow layer of chlo- 



* Herschel found no movements with solutions of caustic alkalies ( Vide Gmeliu's 

 Handbook, vol. i. page 490) ; I have readily obtained them with pure mercury in 

 solutions of pure alkalies by using strong solutions and a powerful electric current, 

 and placing only a small quantity of the liquid above the mercury so as to pro- 

 duce the maximum of effect. Alkaline solutions in general act much more feebly 

 han acids. 



