294 ON THE CALCULATION OF THE CONDUCTIVITY OF 



volume of the solution to be analysed. The following results 

 will show with what accuracy such analyses could be carried 

 out : 



(1.) K 2 S0 4 in 5c.c. of solution = 0.2174 gram. 

 (2.) " " " = 0.2178 u 



(3.) " " " = 0.2179 



Mean = 0.2177 



(1.) Na 2 S0 4 in oc.c. of solution = 0.2365 

 (2.) " " = 0.2369 



(3.) " " " - 0.2370 



Mean = 0.2368 



It would seem that the result might be in error by about 

 0.14 per cent. 



In the case of the Potassium Sulphate, standard solutions 

 were made up from weighed quantities of the salt, which had 

 been dried to constant weight in an air bath. 



Preparation of the Mixtures. 



For convenience in calculating, the mixtures were made up 

 of equal volumes of the constituent solutions. All mixtures 

 were prepared at a temperature of 18C, the constituent solu- 

 tions being kept, for about 20 minutes previously to mixing, in a 

 water bath, the temperature of which was kept as near 18C as 

 possible, by means of a thermostat. A 50 c.c. pipette was used to 

 measure out the volumes ; the same pipette being used for both 

 solutions, and care being taken to use the pipette in the same 

 manner in both cases. During outflow, the point of the pipette 

 was allowed to rest against the side of the vessel, and when 

 outflow had ceased it was slightly blown into without removing 

 the point. 



All pipettes used were calibrated by weighing the water they 

 delivered. None were used in the experiments, in which the 

 time of outflow was less than 40 seconds. 



