296 ON THE CALCULATION OF THE CONDUCTIVITY OF 



and 0.15 per cent at the point farthest from the centre, used in 

 my experiments. 



Platinizing the Electrodes. 



The electrodes, after being washed in boiling alkali and acid, 

 were placed in a solution prepared from a recipe given by 

 Lummer and Kurlbaum, and referred to by Kohlrausch.* This 

 solution consists of 1 part platinum chloride, 0008 of acetate 

 of lead, and 30 of water. They were then connected with the 

 terminals of two Bunsen cells arranged in series, the direction 

 of the current being frequently changed. When the electrodes 

 had become covered with a velvety coating of platinum black, 

 they were removed from the solution and thoroughly washed 

 with boiling water to remove all traces of the chloroplatinic 

 acid. The platinizing can be done much more quickly with the 

 above solution than with the chloroplatinic acid alone. 



Reduction Factor. 



To find the factor, which would reduce the observed conduc- 

 tivities to the standard employed by Kohlrausch, (the conduc- 

 tivity of mercury at O.C), the values of the conductivity for a 

 series of solutions of each salt, which were measured for the 

 purposes of calculation, were plotted against the concentration 

 (gramme-equivalents per litre), and conductivities corresponding 

 to the concentrations examined by Kohlrausch, taken off these 

 curves and compared with the values given by him. The ratio 

 of these values was found to be practically constant for each 

 salt through as wide a range of dilution as it was necessary for 



me to measure. 



Temperature. 



All conductivity measurements were made at 18C. To 

 insure this condition, the cell containing the solution to be 

 measured was placed in a water-bath, the temperature of which 

 was regulated by a thermostat, of the form recommended by 

 Ostwald in his Physico-Chemical Measurements, p. 59, fig. 42. 

 The regulating liquid, which was water, was enclosed in a brass 



* Wied. Ann., LX (1897), p. 315. 





