252 



calcium ; iodide or bromide of potassium ; sulphites of potash or 

 soda; biborate, hyposulphite, or sulphate of soda; sulphate of 

 lime ; arsenic acid ; cyanide of potassium ; oxalate of ammonia. The 

 battery used was a series of 72 small Smee's elements. It appears 

 from these experiments, that the direction of flow obtained by im- 

 mersing the positive wire in the electrolyte and the negative one in 

 the globule is strongly influenced by the chemical composition of 

 the metallic globule. 



42. The chemical nature of the globule exercises an equally 

 powerful influence upon the direction of the movements obtained by 

 the second method. If the mercury was first connected with the ne- 

 gative wire and the solution with the positive wire for a few seconds, 

 and then the connexions reversed or made as in method 2, a temporary 

 and strong positive flow of the electrolyte for a few moments was 

 obtained, apparently in consequence of the mercury absorbing a 

 little alkali-metal or other electro -positive constituent of the liquid, 

 and that substance causing a positive flow of the solution until the 

 whole of it was redissolved. This positive flow did not occur while 

 there was above a certain quantity of the alkali-metal in the mercury. 

 The reversions were obtained in the following liquids : dilute and 

 strong solutions of caustic potash ; weak solutions of caustic soda, 

 baryta, and lime ; carbonate of baryta ; chlorides of potassium, 

 sodium, barium, strontium (not of magnesium, owing to viscosity 

 of the globule), and calcium ; iodide and bromide of potassium ; 

 sulphites of potash and soda ; biborate, hyposulphite, and sulphate 

 of soda ; sulphate of lime ; arsenic acid ; cyanide of potassium ; and 

 oxalate of ammonia ; also in solutions of hypophosphite and diphos- 

 phate of soda ; but not in very dilute nitric acid, nitrates of am- 

 monia, potash, soda, baryta, strontia, magnesia, lime, uranium, zinc, 

 cobalt, nickel, copper, or dioxide of mercury ; sulphates of ammonia, 

 potash, or alumina. It is worthy of notice that these two series are 

 almost precisely the reverse of those named with method 1 (41) ; 

 t. e. those liquids which have the property of reversing the flow of 

 one method have not that property with the other method, except 

 hypophosphite and diphosphate of soda. The explanation suggested 

 (34), of the cause of the true movements of methods 1 and 2 does 

 not appear applicable to these phenomena of reversion. 



43. Herschel has shown that with pure mercury in solutions of 



