Positive Ionization from Hot Salts. G81 



tube of the furnace and the crucible was packed with 

 kieselguhr. It was thought that this arrangement would 

 protect the iron from the action of the air. The projecting 

 end of the crucible was kept cold by means of a water jacket, 

 so as to admit of the central electrode being cemented in 

 with sealing-wax. The central electrode itself was a brass 

 tube 1 cm. outside diameter, closed and tapered at the lower 

 end, and was brazed into a wider tube a little narrower than 

 the steel crucible. The electrode was insulated from the 

 crucible by means of a glnss bush in the sealing-wax joint. 

 It was cooled by a blast of air blown down the inside of it 

 through an axial glass tube, and also by a forced draught 

 driven agaiust brass flanges soldered to the upper projecting 

 parts outside. Water cooling could not be used conveniently 

 as it was necessary to insulate the inner electrode from the 

 crucible. With this arrangement the central electrode was 

 always axial to the platinum tube, and, in sealing it in, matters 

 were arranged so that the end of the brass tube was about 

 6 mm. above the surface of the salt. A side tube leading 

 from the wide part of the inner electrode enabled the 

 crucible and contents to be connected to a Gaede pump and 

 exhausted. 



At room temperatures the apparatus was perfectly air- 

 iight, but at high temperatures a little gas leaked through 

 the hot steel. At 980° C. it was not possible to pump down 

 to less than *006 mm. If the gas thus evolved came from 

 the air outside it would presumably be a mixture of carbon 

 monoxide and nitrogen, since the oxygen of the air would 

 combine with the carbon of the steel during the transference. 

 This leakage was much less at lower temperatures, and it 

 seems highly probable, as most of the experiments were 

 carried out at temperatures under 800° C, that most of the 

 gas which appeared to leak in was evolved by the heated 

 salts. 



Some experiments were also made with a hot platinum 

 electrode insulated on quartz. These were not carried very 

 far as it was found that salt was deposited on the inner 

 electrode, and that there was always a leak both ways which 

 increased rapidly with increasing potential difference. The 

 results of these experiments are difficult to explain, except 

 on the view that when the hot salt is bombarded by positive 

 ions the emission is increased, even when the applied potential 

 difference is considerably less than that required for the 

 positive ions to produce fresh ions by collisions in the ordinary 

 way. 



Preliminary experiments were first made without any salt 



