Electrical Conductivity produced by Heating Salts. 729 



of its quadrants were first connected together and to the 

 insulated pole of the battery H, as in figure 1. The quadrants 

 were then disconnected, one pair being kept on the battery, 

 the other pair to C. A leak of electricity from C is then 

 shown by a constantly increasing deflexion of the electro- 

 meter-needle. The material to be tested was placed in the 

 platinum dish B, which was usually placed in an iron dish 

 so as to prevent those compounds which became liquid at the 

 higher temperatures escaping on to the tube A. 



The temperatures were ascertained by means of a nitrogen- 

 filled mercury thermometer E reading to 360° C. The 

 tube A and its contents were heated by a current passed 

 round the tube through wires insulated from the tube and 

 wound non-inductively. 



In these first experiments the conductivity in cylinder A 

 was measured at atmospheric pressure. 



The following compounds when heated to temperatures 

 not higher than 360° 0. increased the rate of leak of both 

 negative and positive charges from C except in the four 

 cases noted. 



(a) Chlorides of iron (Fe 2 Cl 6 ), aluminium (A1 2 C1 6 ), 



ammonium, magnesium, tin (SnCl 2 + 2H 2 0), man- 

 ganese, and cadmium (C negatively charged). 



(b) Fluorides of calcium, and aluminium (C negatively 



charged) . 



(c) Iodide of cadmium. 



(d) Nitrates of ammonium, cadmium (C negatively 



charged), and cobalt (0 negatively charged). 

 The following substances were tested, but no increased 

 conductivity could be detected when using them : — 



(a) Metals with low melting-point. — Tin, lead, powdered 



bismuth. 



(b) Chlorides of copper, calcium, barium, strontium, 



lithium, potassium, and antimony. 



(c) Iodides of potassium, lead, and silver. 



(d) Bromide of potassium. 



(e) Fluoride of sodium. 



(£) Oxides of copper, zinc, tin, iron, calcium, and mag- 

 nesium. 



(g) Sulphates of zinc, iron, copper, and magnesium. 



(h) Carbonates of zinc, magnesium, potassium, and 

 sodium. 



(i) Bicarbonate of soda. 



(j) Nitrates of lead and barium. 



In these experiments the conductivity was measured hy 

 means of a quadrant electrometer which gave a deflexion of 



