on the Emanation of Phosphorus. 337 



pborns emanation. Permanent leakage due to dislocation of 

 the solid parts was thus out of the question. 



This conduction vanished over night. It was reproduced as 

 soon as fresh phosphorus air passed through the condenser. 

 It then remained permanent though gradually diminishing for 

 hours, and was nearly gone again next day. Hence two causes 

 are suggested : either a film of residual moisture aspirated off 

 from the phosphorus grid (which however was as usual care- 

 fully dried by squeezing in a press between folds of blotting 

 paper, and then exposed to the air, so that only traces of 

 moisture can be in question) was precipitated in the condenser 

 to the detriment of the hard rubber insulation ; or else some 

 form of emanation given off from the phosphorus made the 

 condenser radio active. Incidentally I may advert to the 

 extreme caution needed before such radio-activity can be 

 assumed, the behavior in both cases being essentially alike. 



Warming the condenser seemed to be useless. Moderate 

 amounts of dry air (say 7 liters flowing out in about 10 minutes) 

 passing over the phosphorus were nearly ineffective. It was 

 no remedy to remove the phosphorus and pass dry air alone in 

 the forward direction. Separating the condenser from the 

 water bath did not change its conduction. Thus I found, for 

 instance, for the condenser alone and free from air current, 

 ds/dt = 33 ; an hour later, ds/dt = 25 ; next day ds/dt = 7 ; 

 good insulation, ds/dt = 2. 



^At 6 = 30° (water bath temperature), the tendency of the 

 condenser to conduct permanently was at first accentuated but 

 soon completely wiped out. The electric current reached a 

 normal value. This appeared so much like a moisture error 

 that I further teated it by passing the air current backwards, 

 through the condenser first and then over the phosphorus into 

 the atmosphere, in this way drying both parts. Insulation of 

 the condenser was thus at once restored. Again on passing a 

 considerable volume of dry air (say 15 liters, slowly) over the 

 phosphorus, this too lost its power to make the condenser 

 permanently conducting. Hence in the experiments of the 

 following table the phosphorus was first dried in this way in a 

 current of dry air. The work then progressed smoothly, show- 

 ing the relation of the emanating activity of phosphorus to 

 temperature in a new light. 



I may add again that in none of my earlier experiments 

 were like discrepancies encountered. Possibly a corroded 

 copper grid may be hygroscopic, something like platinum 

 black. 



16. /Specially dried phosphorus grids. — In Table IY, is 

 the temperature of the water bath, d V/dt the volume of dry 

 air in liters passed per minute over the phosphorus : ds/dt is 



