AQUEOUS SOLUTIONS. ARCHIBALD. 297 



tube, about .'35 cm. long and 4 cm. in diameter, bent so as to 

 form three sides of a square. Two vanes fixed at an angle of 

 45 near the bottom of the bath, to a vertical axis, which was 

 turned by a small hydraulic motor, kept the water of the bath 

 well stirred. The thermometer used was graduated to fiftieths 

 of a degree, and could easily be read to hundredths. Its readings 

 were compared with those of another, whose errors had recently 

 been determined to hundredths of a degree at the Physikalisch- 

 Technische Reichsanstalt, Berlin. With this apparatus the 

 temperature of the bath could be kept constant to within a 

 fiftieth of a degree, for half an hour at a time. A variation of 

 one-fiftieth of a degree might cause an error of 0.05 per cent in 

 the determination of the resistance. 



That one might be sure that the temperature of the solution 

 to be measured had come to be that of the bath, two or more 

 determinations of the resistance were always made at intervals 

 of about five minutes, and that reading taken which was found 

 to be the same for successive intervals. 



Data for the Calculations. 



For the simple solutions the ionization coefficient () was 

 taken to be equal to the ratio of the specific molecular conduc- 

 tivity to the specific molecular conductivity at infinite dilution. 

 Kohlrausch's values for the specific molecular conductivity at 

 infinite dilution were used. They were taken to be 1280 x 10~ 8 

 and 1060 X 10~ 8 for Potassium and Sodium Sulphate respectively, 

 as determined by him.* 



The value of p in the above formula was found by density 

 measurements before and after mixing. These measurements 

 were carried out with Ostwald's form of Sprengel's pyknometer. 

 Measurements, accurate to one in the fourth place of decimals, 

 which was bej^ond the degree of accuracy required, could be 

 made without much difficulty. The value of p was found to be 

 practically equal to unity for the most concentrated solutions 

 examined. 



* Wied. Ann., Vol. xxvi., p. 204. 



