On the Movements of Liquid Metals in the Voltaic Circuit. 161 



metallic globule upon the movements obtained by the 1st method, in 

 the following manner. The globule of mercury was first connected 

 with the positive pole and the liquid with the negative pole for about 

 ten seconds, and then the wires placed as in method 1 ; a temporary 

 negative flow was produced for a few moments with certain liquids, 

 apparently in consequence of the mercury absorbing a minute portion 

 of an electro-negative constituent of the solution (?), and that sub- 

 stance causing a negative flow in the succeeding operation until the 

 whole of it was redissolved. The following liquids exhibited this 

 phenomenon of reversion : — very dilute solutions of nitric acid, nitrates 

 of ammonia, potash, soda, baryta, strontia (not of magnesia, appa- 

 rently on account of viscosity of the mercury being produced), lime, 

 zinc, lead, cobalt, nickel, copper, and dioxide of mercury; also 

 sulphates of ammonia and potash ; hypophosphite and diphosphate 

 of soda ; and, strongest, the alkaline nitrates ; — but not dilute solu- 

 tions of caustic potash, soda, baryta, or lime ; carbonates or bi- 

 carbonates of potash or soda ; carbonate of baryta ; chlorides of 

 ammonium, potassium, sodium, barium, strontium, magnesium, or 

 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) ; 

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



