WORK OF McMASTER. 



EXPERIMENTAL. 



APPARATUS. 

 CONDUCTIVITY. 



The Kohlrausch method of measuring conductivity, with a Wheatstone 

 bridge, telephone receiver, and induction coil, was employed. The bridge- 

 wire was of "manganin" and was calibrated before beginning the work by 

 the method of Strouhal and Barus. 1 



The resistance coils were carefully calibrated. 



The conductivity cells were of the form used by Jones and Bingham. 2 

 In order to work with the alcohols and acetone, it was necessary to use cells 

 of this form. They were made of hard glass, with ground-glass stoppers. 

 The glass tubes carrying the platinum electrodes were sealed into both the 

 upper and lower walls of the stopper. By using such cells, the presence of 

 rubber or wax, which would be dissolved by the solvent, was avoided. They 

 also prevent evaporation of the more volatile solvents, and protect the anhy- 

 drous alcohols and acetone from the moisture of the baths and air. 



The electrodes were treated in the manner recommended by Whetham. 3 

 They were first coated with platinum black and then heated in the flame of a 

 blast-lamp. Electrodes covered with platinum black absorb a small amount 

 of salt from the solution, and give up some of it again when water or a more 

 dilute solution is placed in the cell. The gray platinum formed by the heating 

 process does not absorb an appreciable amount of salt, and the oxidizing action 

 of platinum black is also avoided by this treatment. 



The zero-bath consisted of an inner and outer vessel. The inner vessel 

 and the space between the two were filled with finely crushed, pure ice, mois- 

 tened with distilled water. The 25 bath was of the usual form, the stirrer 

 being driven by means of a hot-air engine, or a Rabe water turbine. The 

 Ostwald thermoregulator was used. The thermometers employed were accu- 

 rate to a tenth of a degree. Burettes and flasks were carefully calibrated, 

 according to the method of Morse and Blalock. 4 



VISCOSITY. 



The apparatus used was of exactly the form described by Ostwald and 

 Luther. 5 A fixed volume of the liquid, the viscosity of which was to be 



l Wied. Ann., r 10, 326 (1880). 4 Amer. Chem. Journ., 16, 479 (1894). 



2 Amer. Chem. Journ., 34, 493 (1905). 6 Physiko-Chemische Messungen, II. 

 s Phil. Trans., 94A, 321 (1900). Aufl., p. 260. 



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