Constant* of certain Organic Bodies at Low Temperatures. 359 



We have now examined, in addition, the following organic bodies, 

 viz., formic acid, methyl alcohol, amyl alcohol, acetone, chinoline, tetra- 

 ethylammonium hydrate, and carbolic acid, and we find that these 

 bodies have, in the liquid or solid condition and at temperatures 

 above —100° C, high, or very high, dielectric values, but all have 

 their dielectric constants reduced to a value not far from 2*5 when 

 they are cooled to the temperature of liquid air. 



In addition, we have measured the dielectric constants of castor oil 

 and olive oil, and find that they are reduced in value when these oils 

 are cooled to —185° C. We have also measured the dielectric 

 constants of bisulphide of carbon, ether, ethyl nitrate, solution of sulphur 

 in bisulphide of carbon, and absolute alcohol with 10 per cent, of 

 metallic sodium in it. We find in all these cases that there is a reduc- 

 tion in the value of the dielectric power, large or small, these bodies 

 possess at normal temperatures. These experiments further confirm 

 the view that the presence of the radicles hydroxyl (HO), carbonyl 

 (CO), and the organic acid radicle (COOH) always produce relatively 

 high dielectric values in the bodies containing them when these 

 bodies are in the. liquid condition or at temperatures not very far 

 below their freezing points. When these bodies are, however, frozen 

 and cooled to the temperature of liquid air, all of them suffer a 

 reduction in dielectric power, and their dielectric constants are 

 reduced to values not far from 2*5, or between 2*5 and 2*6, at the 

 temperature of —185° C. or a little below. The action of the low 

 temperature is thus to annul the effect of the radicle. 



We have not found, so far, any exception to the rale that pure 

 organic bodies have a dielectric constant of from two to three times 

 that of vacuous space when they are cooled to the temperature of 

 boiling liquid air, no matter what value their constant may have 

 when in the liquid condition. 



The following tables give the numerical results, and the observa- 

 tions are delineated graphically in the chart in fig. 1. 



All the tables are headed by a statement giving the galvanometer 

 scale deflection in centimetres when the condenser has air as dielec- 

 tric. This is to be understood as the constant, for the time being, 

 representing the capacity of the condenser when its dielectric is 

 gaseous air at normal pressure and temperature. The numbers in 

 the columns headed " Dielectric constant," under each substance are 

 obtained by dividing the number in the second column of the tables, 

 headed "Mean galvanometer deflection," by the above air capacity 

 constant, after having applied a correction to the galvanometer 

 reading for the charging voltage and for the capacity of the leads. 

 The numbers headed " Mean galvanometer deflection," when corrected 

 for voltage and the capacity of the leads and vibrator, represent, to 

 the same scale as the corrected air capacity constant, the capacity 



2 c 2 



