OF SALTS IN ETHYL ALCOHOL AND WATER. 85 



The proper corrections have been applied to the data in the following 

 tables. The difference between the density at 20 and at the other 

 temperature in question was determined. This difference represents 

 the decrease or increase in volume per cubic centimeter of the solution. 

 Subtracting the decrease below 20 from 1.0 and adding it to 1.0 above 

 20, gives the coefficient of contraction or expansion respectively. 

 Since at 15 the volumes of the solutions become smaller, there is a 

 decrease also in the molecular conductivities. At 25 and 35 the 

 expansion, bringing about an increased volume normality, results in a 

 positive correction to the conductivity. 



VISCOSITIES. 



The viscosity apparatus used in this investigation was essentially 

 the same as that described by Davis and Jones 1 in their work on glycerol. 

 The viscosimeters were of the general type therein described, the capil- 

 lary tubes having a diameter of about 0.5 mm. Some improvements 

 were made in connection with the constant-pressure apparatus for 

 elevating the liquid to the upper mark on the capillary limb of the 

 viscosimeter, and special precautions were taken to dry the air thor- 

 oughly by passing it through a long drying-tube filled with calcium 

 chloride. By means of dust-traps filled with cotton, clogging of the 

 capillary was effectively prevented. 



The desk supporting the viscosimeter stand was not connected 

 with the supports for the motor and stirrers. This was to avoid the 

 vibration due to the motor, and was secured by attaching the motor 

 support directly to the walls of the building. To reduce the vibra- 

 tions still further, the stand holding the viscosimeter rested on several 

 layers of felt. 



The stand itself consisted of a heavy tripodal base, with a three- 

 quarter-inch bronze standard, to which a heavy horizontal arm was 

 attached by means of a set-screw. The viscosimeters were fastened to 

 the arm by means of a spring clamp, the tension of which was adjusted 

 by a thumb-screw. The stand was carefully leveled by means of 

 leveling screws, at right angles to the line of sight in reading the visco- 

 simeter. Leveling in the other direction was accomplished by sighting 

 along the vertical arm of the viscosimeter to a plumb-line suspended 

 before the glass window in the bath. 



Temperature regulation in the viscosity work was essentially the 

 same as that in the conductivity. By means of the mercury regulator 

 (fig. 34) already described, the temperature was kept constant for any 

 desired length of time to within 0.01 at 15 and 35, and to within 

 0.005 at 25. 



!Zeit. phys. Chem., 81, 68 (1912). 



