Constants of certain Organic Bodies at Low Temperatures. 367 



Dielectric Constants of some Organic Bodies at Normal and at very 

 Low Temperatures for Low Frequencies. 



I 



Substance. 



Methyl alcohol 



Ethyl alcohol 



Amyl alcohol 



Formic acid 



Acetone 



Ethylic ether 



Castor oil 



Olive oil 



Bisulphide of carbon 



Aniline 



Carbolic acid 



Ethyl nitrate 



lated by Cauchy's formula for infinite wave-lengths, on the assump- 

 tion that there is no anomalous dispersion. 



The determination of the actual values of the refractive indices of 

 these bodies at the liquid air temperature is a work of great diffi- 

 culty, and one which we have not yet attempted. There is no question 

 that it is important also to determine whether these very low 

 temperatures have any effect in altering the absorptive power of these 

 organic bodies for ultra-red rays, and removing that anomalous dis- 

 persion which appears to exist in some of them beyond the limits of 

 the visible spectrum. 



We are much indebted to Mr. J. E. Petavel for assistance in the 

 work of taking the above described observations. 



Dielectric constant (K) 



at 15° C. 



34 -0 (Thwing) . 

 25 -8 (Nernst) . . 

 16-0 (Nernst).. 

 62-0 (Thwing). 

 21-85 (Thwing). 



4 -25 (Nernst) . - 



4'78 (Hopkinson) 



3-16 



2 -67 



7 -51 (Smale) 

 17 -72 (Thwing) . . 



at - 185° C. 

 (Dewar and 

 Fleming.) 



313 

 3-11 

 2-14 

 •41 

 •62 

 •31 

 •19 

 •18 

 •24 

 2 92 

 2-54 

 2-73 



(Infinite 

 Kef'ractive In- 

 dex) 2 = (fi^y 



1 -831 

 1-951 



1- 805 



2- 153 

 2-131 

 2-010 



