132 ON THE CALCULATION OF THE CONDUCTIVITY 



Experimental Methods. 



The hydrochloric acid was obtained from Eimer & Amend, 

 and the sulphuric from Merck & Co. Both were guaranteed 

 chemically pure. The redistilled water used in the preparation 

 of the solutions was obtained by the method described in 

 a former 1 paper, and it had a conductivity ranging from 

 0.95 x 10~ 6 to 1.01 X 10~ 6 expressed in 2 Kohlrausch's new unit 

 (ohm" 1 cm." 1 ). 



The amount of hydrochloric or sulphuric acid in a solution 

 was determined volu metrically by means of aqueous solutions of 

 potassium hydroxide, the strength of these being determined 

 daily by titration with known quantities of dry oxalic acid. 

 Phenol-phthalein was the indicator used. The potassium 

 hydroxide solutions were kept in bottles with stoppers, each 

 containing a soda lime tube. The pipettes, burettes and flasks 

 were calibrated and used as described in the paper referred to 

 above. The specific gravity at 18C. was determined for many 

 of the simple solutions with a pyknometer of the Ostwald- 

 Sprengel form. The comparison of the values thus obtained 

 with the values as given by Kohlrausch, acted as a check upon 

 the concentration as determined above. 



Kohlrausch's method with the alternating current and tele- 

 phone was employed in the measurement of the conductivity. 



The bath used to obtain a constancy of temperature, for a 

 time sufficient to make the determination of the resistance in, 

 contained tap water kept continually stirred by a mechanical 

 stirrer driven by one of Henrici's small hot air motors. This 

 motor worked without noise and on this account was found 

 more serviceable than the hydraulic motor formerly employed. 

 The thermometer used could be read to a hundredth of a degree, 

 and had been tested at the Physikalisch-Technische Reichsanstalt, 

 Berlin. 



The resistance of the solutions was measured in a U-shaped 

 cell having electrodes of stout platinum foil connected by thick 



'Trans. N. S. lust. Sci., 10, 49, 1898-9. 



* Kohlrausch u. Holborn : Leitvermogen der Elektrolyte, 1898, p. 1. 



