247 



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, -j- being po- 

 sitive and -j- 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 : 



. -* faint 



Distilled Water 



Boracic Acid 



Phosphoric Acid 



Strong Sulphuric Acid. . . 

 Strong Sulphuric ~| 



Acid 1 measure I 

 Water 5 j 

 Strong Sulphuric "1 



Acid 1 measure j. 

 Water 15 J 

 Strong Hydriodic "J 



Acid 1 measure L 

 Water 15 J 

 Hydrobromic Acid, 



very dilute 



Strong Hydrochloric "J 



Acid 1 measure L 

 Water 5 j 

 Strong Hydrochloric 1 



Acid 1 measure I 

 Water 15 j 

 Perchloric Acid, very 



dilute 



Strong Hydrofluoric Acid 



2 



-j- 4 



H- 4 



Strong Hydrofluoric ~\ 

 Acid 1 measure , 



Water 5 j 



Strong Nitric Acid, ~| 

 1 measure 1 



Water 1 J 



Strong Nitric Acid, "1 

 1 measure I 



Water 5 J 



Strong Nitric Acid, ~| 

 1 measure I 



Water 15 J 



Aqueous Ammonia, 

 strong 



Sesquicarbonate of Am- 

 monia 



Phosphate of Ammonia . 



Sulphide of Ammo- ~\ 

 nium, 1 measure" 



Water 15 J 



Sulphate of Ammonia . . . 



Hydrochlorate of Am- 

 monia 



Nitrate of Ammonia 



Caustic Potash . . . 



