of Organic Bodies, Sfc, at very Low Temperatures. 257 



question whether there was any sensible or serious lag in the tem- 

 perature of the resistance thermometer behind the temperature of the 

 dielectric. Our usual custom had been to immerse the condenser 

 when prepared for use in liquid air, and cool down the whole mass 

 to —185° C, and then raising it out of the liquid air to take tem- 

 perature and capacity readings as it warmed up. The resistance 

 thermometer was placed in the inner cone in a thin test-tube, and 

 fixed in with fusible metal in the inner cone. We therefore tried 

 one experiment with pure glycerine as dielectric, in which the 

 electrical measurements were made as the condenser was slowly 

 cooled, instead of being made as it slowly heated up. The process 

 of cooling from —38° jpt. to —201°pt. was allowed to occupy one 

 hour and forty minutes. The values thus found for the dielectric 

 constant for glycerine for this range of temperature were practically 

 in agreement with those found when the condenser capacity was 

 measured as it warmed up instead of cooled down. 



Table VI. 



I. Dielectric Constant of Pure Glycerine. 



Corrected galvanometer deflection when the condenser had air as 

 dielectric == 3*92 cm. for 100 volts. 



Mean 



Temperature galvanometer 

 in platinum deflection Dielectric 

 degrees. in centimetres, constant. Observations. 



—38-0 2-85 50-5 Coudenser charged with 1-434 



—42-6 2-97 52-8 volts. Time = 3.5 p.m. 



-46-0 3-00 53-3 



-55-8 3-17 56-5 



-64-8 3-03 53-8 Time = 4.15 p.m. 



-98-8 2-70 3-95 Condenser charged with 17"0 volts. 



-119-5 2-20 3-19 Time = 4.30 p.m. 



-201-0 11-05 2-82 Condenser charged with 92*4 volts. 



Time = 4.45 p.m. 



The above values of the dielectric constant of glycerine are in 

 very fair agreement with the values obtained by us during rising 

 temperature.* 



We have also extended our former observations made w 7 ith this 

 cone condenser and the galvanometric method to certain other 

 frozen electrolytes, and measured their dielectric constants at low 

 temperatures. 



The results and substances are as follows : — 



* ' Eoy. Soc. Prcc.,' vol. 61, p. 324. 



