832 Mr. R. T. Lattey on the Dielectric 



the true value of 0, and that such experiments will give too 

 high a value for the dielectric constant of the substance 

 under investigation unless proper corrections are applied. 



Comparison of the charges imparted to two condensers by- 

 an alternating E.M.F. will require correction depending on 

 the inductance aud resistance of the leads between the con- 

 densers. The most complete series of observations of this 

 kind is that carried out by Smale 52 , and his results lor the 

 ratio of the dielectric constants of certain solutions to that 

 of water are given in Table I. 



Table I. 



Ratio of D.C. for Solutions to that of Water (Smale). 



Normality 0-001 0-002 0-005 0-008 0-010 0'020 0"030 0-050 



Solute HC1 ,0-99 1-033 1-064 1-090 1-126 



KC1 1-013 1-018 1-034 1-070 1-113 ... M60 



0uSO 4 1-012 1017 1050 T086 1-128 ... T155 



The apparent rise in the D.C. due to dissolving an elec- 

 trolyte in water is most marked in the case of the best 

 conductor (HC1), and increases as the strength of the 

 solution increases. It will be seen from what follows 

 that the true D.C.'s for these solutions are probably less 

 than that of water. 



B. Tuning by altering tlie size or the distance between the 



plates of the condenser. 



As the capacity is increased, the resistance will diminish 

 in such a way that the product Cr remains constant. The 

 condition that Z in equation (1) may be a minimum is 

 then p 2 CL = l+R/?', or, using the same notation as before, 

 C = C 1 (l + E/r), and the uncorrected values of the D.C. of 

 a solution obtained in this way will be lower than the 

 true values. The method was used by Marx 39 , but was 

 only applied to water of low conductivity — i. e., the 

 ratio ~R/r was negligibly small. 



C. The electrolytic condenser is connected in parallel with a 



variable air condenser, and tuning obtained by varying 

 the latter. The electrolytic condenser is then removed 

 and the air condenser readjusted. 



This was the method used in the present work. The 

 essential features of the circuit are shown in fig. 2. Oscil- 

 lations were induced by a neighbouring circuit emittino- 



