ELECTRO-CHEMISTRY. 1 1 



wires were introduced into a small bent tube, ex- 

 ternal of the tray, containing a solution of the iodide 

 of potassium (Ficj. 2). After the tray had been 

 brought to a red heat, the solution itself being kept 

 at a low temperature, the iodide was decomposed ; 

 the iodine appearing in the limb of the bent tube, 

 into which" was introduced the extremity of the 

 wire which projected from the tube in the tray that 

 contained the acid. It is evident that electricity was 

 the agent by which the iodide was decomposed, and 

 as the iodine appeared in the limb of the tube into 

 which the wire from the acid was introduced, the 

 positive electricity was derived from the acid, and 

 consequently the negative electricity from the metal. 

 In like manner, a solution of the iodide of potassium 

 contained in a similar bent tube, was decomposed by 

 a water battery, the iodine appearing in the limb of 

 the tube into which the positive wire of the battery 

 was introduced. 



10. Exp. 2. December 18, 1857- 



The iodide of potassium, decomposed by electri- 

 city, of which the positive electricity was derived 

 from nitric acid, and the negative electricity from 

 potassium. 



Two grains of nitric acid were introduced into 

 one of the tubes, and an equivalent quantity of 



