Ionization! from Certain Hot Salts. 237 



When touched by a Pt wire between readings the emis- 

 sion at 1150 was increased only 10 per cent., which can be 

 accounted for simply by the exposure to the air in taking 

 out the strip. 



The distilled water was made in a block tin vessel and 

 kept in a bottle washed repeatedly with distilled water, but 

 not boiled. It was the same water which was used in 

 laving the various salts on the Pt strip in the previous 

 experiments. 



Measurements on mjH from the strip (see above) : 



(A) V. H. M. T. m/H. 



203 2460 B 1027° 40-1 Pt strip after long 

 „ „ „ 1090° 36*7 exposure to air. 



Strip glowed out to 1100°. 



(B) V. H. M. T. m/H. 



204 2460 B 930° 37-7 Strip plus distilled 

 „ „ „ 933° 36-7 H 2 0. 



From these investigations of the sources of impurities in~ 

 handling the apparatus it appears that the salts which it 

 was possible to mount on the strip dry were practically un- 

 contaminated, as far as the process of mounting went. The 

 only chance l'or impurity not already in the salt would be a 

 very slight amount from exposure to the air. 



As for the salts mounted with water, if no emission below 

 800° could be obtained sufficient to take readings, the chances 

 are that the emission from the water would figure largely in 

 the results. By emission from the water of course emission 

 from impurities brought in with the water is meant. If 

 emission was obtained at temperatures below 700°, it is 

 likely that the emission due to the water would not enter 

 into the results. 



A very noticeable characteristic of these impurities is that 

 they are not at all lasting. The decay was found to be quite 

 rapid for every case except the one where the Pt strip was 

 exposed to the air for 42 days. In this case the emission 

 was found to increase considerably at constant temperature 

 for a short time after heating was begun. 



7. Molybdenite. 



This mineral appeared to be well adapted for measure- 

 ments with this apparatus. It occurs in the form of flat 

 sheets, rather soft, of a metallic lustre, and very sectile. 



