Ionization from Certain Hot Salts. 231 



About twenty readings were taken, which ran from about 

 35 at 900° to 32*5 at 1100°. The few readings taken by the 

 slit method gave values around 32*5, except one at 900°, 

 the only one taken below 1100°, which gave 35*9. 



Conclusion. — From these values of m/H it certainty would 

 seem as if a Cu ++ ion had been detected. The first specimen 

 (a) evidently was not at all pure, but there were signs of a 

 doubly charged ion at high temperatures. When emission 

 first set in with (b) the values were uncertain. At the higher 

 temperatures there are still more positive evidences of a 

 Cu ++ ion, for which ??i/H = 31*6. 



In any case there is probably no emission of Gu-ions under 

 1000° or so. At this temperature and pressure, however, 

 the salt must long since have been vaporized. If there is 

 an emission of Cu-ions then, it seems likely that it must 

 come from the action of the Pt on the vapour. This was 

 shown to be possible by Sheard *. 



Cupric Chloride : CuCl 2 , 2 H 2 0. 



(c) This salt was probably very pure — Kahlbaum, kryst, 

 " zur Analyse." Its melting point is 498° C. At 100° 

 CuCl 2 with water of crystallization loses half its chlorine to 

 form Cu 2 Cl 2 . This action was confirmed. 



The Pt strip, mounting (b) , on which measurement was 

 made had been glowed below 1100°. Emission from the 

 salt was first detected at 780°. A great deal of trouble was 

 experienced in keeping it on the strip when dry. 



V. H. M. T. elm. m/H. 



840° 



204 2460 B & S to 266-3 36-3 dry crystals. 



1200° 



870° 



204 2460 B to 266-3 36-3 „ „ 



1050° 



Conclusion. — This does not seem to be anything more than 

 the regular impurity emission. The value is, however, a 

 little low. As CuCl 2 is supposed to go over into Gu 2 Cl 2 at 

 500°, this may be taken as evidence that the emission from 

 Cu 2 Cl 2 in (a) and (b) above is not characteristic Cu emission, 

 but a combination of K and Na impurities for instance. 

 Nevertheless, it is difficult to ascribe the very distinct values 

 about 32 to an increase in the distance d. 32 as a low value 

 for 39 is perhaps possible but not probable. It may thus be 

 that the value 36*3 in (c) was due to a mixture of Cu ++ and 

 K + ions. In that case a characteristic Cu ++ emission would 

 take place in both cases. At all events there certainly is no 

 sign of a singly charged ion of Cu. 



* Phil. Mag., March 1913, p. 370. 



