On the Movements of Liquid Metals in the Voltaic Circuit. ]57 



the act of deposited substances dissolving in the mercury, for they 

 occur equally well whether hydrogen gas is set free and escapes or 

 alkali-metal is deposited and dissolves in the mercury, until in the 

 latter case the diminished mobility of the globule interferes with the 

 result. 



33. Considerable difficulty was experienced in examining liquids 

 by the second method, in consequence of the rapid and in many cases 

 instantaneous oxidation or filming of the metallic globule ; but by 

 using very dilute liquids and immersing the negative wire from 

 seventy-two small Smee's elements during only a moment at a time, 

 this difficulty was in most cases sufficiently overcome to allow di- 

 stinct starts of the mercury to occur in the particular direction 

 beneath its film, and thus to indicate an opposite motion of the 

 supernatant liquid, although in nearly all cases the movement of the 

 electrolyte itself could not be detected. Upwards of 100 liquids, 

 consisting of organic and inorganic compounds — acid, alkaline, and 

 neutral — were examined, and in more than three-fourths of them di- 

 stinct movements of the metal were obtained, which were in every 

 instance in a positive direction, thus indicating a negative flow of 

 the electrolyte. In some liquids, viz. oil of vitriol, moderately di- 

 lute nitric acid, strong solutions of sulphate of ammonia, iodide of 

 ammonium, and sulphite of potash, very dilute solutions of bisul- 

 phate of potash, iodide of potassium, nitrate of cobalt, hydro- 

 cyanic acid, cyanide of potassium, and acetic acid, — visible move- 

 ments of the liquid itself in a negative direction were also ob- 

 tained. The movements of the liquid and of the metal very quickly 

 ceased. These experiments show that the direction of flow ob- 

 tained by placing the positive wire in the metal and the negative 

 wire in the electrolyte is always negative. 



34. The movements obtained both by methods 1 and 2 appear to 

 be produced by a mutual attraction of the liquid and metal ; in the 

 former case the mercury attracts an electro-positive element of the 

 liquid (hydrogen or an alkali-metal), and produces a positive flow ; 

 and in the latter case it attracts an electro-negative element (generally 

 oxygen), and produces a negative flow. 



35. Herschel found by the third method of operating, that with 

 pure mercury in acids and saline liquids the flow was negative, and 

 was weaker as the base was stronger, and more rapid as the acid was 

 stronger and more concentrated ; and that in solutions of nitrates 

 two opposite flows occurred, one from each wire {vide Gmelin's 

 Handbook, i. 490). I have found by an examination of pure 

 mercury in various liquids the results exhibited in the following Table. 

 The arrows indicate the direction of flow of the liquid, -{- being po- 

 sitive and -¥ negative ; and the numbers affixed to them afford a 

 rough approximation of the velocity or magnitude of the movements. 

 The battery employed consisted of twenty-two small Smee's elements. 

 The substances were^dissolved in water, and the solutions were of mode- 

 rate strength unless -otherwise stated. Manifestly impure substances 

 were rejected, and fresh mercury was taken for each experiment. 

 The results obtained were in many cases verified several times : — 



