118 WORK OF E. G. MAHIN. 



sarily made. We have, however, followed the latter method, making each solution 

 from the one next higher in concentration. 



APPARATUS. 



In making conductivity measurements Kohlrausch's method was used, the Wheat- 

 stone bridge, induction coil, resistance coils, and telephone being made by Leeds and 

 Company, of Philadelphia. The resistance coils were found to be accurate to within 

 0.04 per cent. For high resistances, two sets of coils were placed in series, giving 

 a total available resistance of 42,000 ohms. The bridge wire was calibrated by the 

 method of Strouhal and Barus. 1 For compensating the electrostatic capacity of 

 the conductivity cells when measuring high resistances, a condenser was used, con- 

 sisting of two brass plates, sliding over each other and separated by a thin sheet of 

 paraffined paper. The conductivity cells were those described by Jones and Bing- 

 ham, 2 and the resistance capacity was determined by the use of 0.02 normal and 

 0.002 normal potassium chloride solutions, 129.7, the value given by Ostwald, 3 

 being taken as the molecular conductivity of the 0.02 normal solution. The elec- 

 trodes were platinized before using, by electrolysis of a dilute solution of platinum 

 chloride in the cell, after which they were heated in the flame of a blast-lamp until 

 whitened. After using a given solution the cell was thoroughly washed out and 

 allowed to stand filled with distilled water for at least a day; it was then dried by 

 means of alcohol. We satisfied ourselves, by repeated tests, that this method of 

 drying did not produce acid on the electrodes. Measurements were made at 

 and 25. The thermometers were graduated in 0.2 intervals, and were compared 

 with a thermometer that was certified by the Reichsanstalt. 



Viscosity measurements were made by means of a modified form of the Ostwald 

 viscosimeter. 4 The modification has been described by Jones and Veazey. 3 Vis- 

 cosity was calculated from the formula 



ST 



OOi 



in which 77 is the viscosity coefficient for the fluid in question, 770 is the viscosity 

 coefficient for water at the temperature at which the experiment is being carried out, 

 S is the specific gravity of the solvent or solution, T is the time of flow of the solvent 

 or solution, So is the specific gravity of water at the given temperature, and To is 

 the time of flow for water. Fluidity was calculated from the formula 



.,. 1 



Fluidity = $ = - 



The viscosity coefficients for water which were used in the calculations are those 

 taken from the researches of Thorpe and Rodger. 6 Specific gravities were deter- 

 mined by the use of the picnometer described by Jones and Veazey. The visco- 

 simeters and picnometers were made for us by Eimer and Amend of New York. 



'Wied. Ann., 10, 326 (1880). 'Lehrbuch. 2 Aufl.. S. 732. 'Zeit. phys.Chem.,61,641 (1908). 



-Amer. Chem. Journ.,34, 493 (1905). Physiko-ChemischeMessungen,2 Aufl., S.259. 'Phil. Trans., 185 (A), 307 (1894). 



