34 Conductivity of Aqueous Solutions. Part II. 



to the temperature of the bath, this correction is different for different 

 temperatures. This resistance may be considered as made up of three 

 parts : R 1} the constant resistance of the heavy leads ; R 2 , the resistance of 

 the small leading-in wires, L x and L, ; and R 3 , that of the steel electrode 

 rod. R t and R 2 were measured at room temperature. For the other tem- 

 peratures R 2 was calculated from its value at room temperature. R 3 was 

 calculated from its dimensions and the specific resistance of steel. The 

 maximum value (at 306) of the total resistance of the lead-wires was 

 0.061 ohms. 



(6) In the case of the more dilute solutions it was necessary to correct 

 for the conductance of the water used. To do this, some water prepared 

 in the same way and of the same conductance cold as that used for making 

 up the solutions was put into the bomb, and just such a set of experiments 

 was made with it as had been made with the solutions. Then for any tem- 

 perature the conductance of the water, measured at that same temperature 

 and under the same conditions, was deducted from that of the solution. 

 This at the same time corrects for contamination, since, with a dilute, 

 neutral-salt solution, there is no apparent reason why the contamination 

 should not be the same as for water. For the most dilute solution used, 

 0.0005 normal, the maximum correction (at 30G) amounts to 1.9 per 

 cent. See also section 14. 



(7) In the conductivity experiments, the vapor space at 140 and 218 

 was considerable, so that at these temperatures a correction has to be 

 applied for the vaporized solvent, since the solution is more concentrated 

 than it would otherwise be. This correction was calculated from the 

 known volume of the vapor in the bomb and its specific volume, using for 

 the latter the data of Zeuner* which go up to 200, and extrapolating for 

 the 218 value. The correction amounts to -\- 0.05 per cent at 140 and 

 -f- 0.18 per cent at 218. As explained above, it is not required in the 

 case of the 281 and 306 values. 



(8) The temperature measurement at 26 is certainly more accurate 

 than the work requires. Above this, the temperature reading is probably 

 correct to 0.2. Most of the uncertainty in the equivalent conductance 

 values introduced by this possible error finds expression in the specific- 

 volume values, and this has already been considered. Besides this there 

 is the much smaller effect on the observed resistance of the bomb. The 

 total uncertainty in the equivalent conductance arises from both these 

 sources; that due to 0.2 is in the worst case (at 218) 0.09 per cent, and 

 where, as has usually been the case, several experiments are made and 

 the mean taken, this effect tends to be eliminated. 



*Landolt-B6rnstein-Meyerhoffer, Tabellen, 62 (1905). 



