388 Intelligence and Miscellaneous Articles. 



ON THE DETERMINATION OF THE DIELECTRIC CONSTANT OF 

 CONDUCTING LIQUIDS. BY W. STSCHEGTIAEFF. 



To avoid the errors caused by absorption and the conductivity of 

 the dielectric, it is necessary to use electrical oscillations of as short 

 period as possible, or to arrange the experiment so that the errors 

 mutually compensate each other. The author prefers the second 

 method. The condenser is formed of three disks, two of which 

 are fixed vertically at 5 millim. from each other, and the third can 

 be displaced parallel to itself, this latter and one of the two fixed 

 disks are connected with the electrodes of a TCuhmkorff, while the 

 central disk is put to earth through a sort of Geissler's tube formed 

 of a small incandescent lamp of 5 volts, the filament of which has 

 been broken by too strong a current. This apparatus placed quite 

 near the disk is extremely sensitive to electrical oscillations, the 

 presence of which is shown by a light like that of Geissler's tubes, 

 while the static discharge of the condenser produces a spark. 



If the two extreme disks are not arranged so as to form two 

 condensers of equal capacity with that of the middle, this latter is 

 charged and the lamp is illuminated ; by varying the distance of 

 the movable disk this light can be annulled ; it reappears when 

 the desired position has been passed. In order to diminish this 

 error the mean a of the two distances is taken. If between the two 

 stationary disks of the condensers a layer of a dielectric of thick- 

 ness d is interposed the constant of which is D, the movable disk 

 must be displaced through a length x in order to make the light 

 disappear. We have the equations 



j , d -p. d 



D d — x 



The liquids were placed in a glass trough with parallel sides. 

 The results obtained are in agreement with Maxwell's law : 

 V jj=» oo . 



D. VD. n oo . 



Glass 2-263 1-503 1-538 



Benzole 2-17 1-473 1-476 



Water 1*75 1-323 1-323 



Alcohol 1-62 1-273 1-353 



Methylic alcohol 2-21 1-487 1-397 



Journal de la Societe Physico-chimique Russe, vol. xxiii. 1891 ; 

 from Journal de Physique, June 1892. 



