116 CONDUCTIVITY AND VISCOSITY IN MIXED SOLVENTS. 



ETHYL ALCOHOL. 



The best commercial article was treated in the same manner as the methyl 

 alcohol. Its conductivity at was about 0.0 X 10~ 7 . 



ACETONE. 



The acetone was allowed to stand over fused calcium chloride before using. 

 Conductivity at 0= 1.0 x 1Q- 6 . 



MIXED SOLVENTS. 



The mixture obtained by adding n c. c. of solvent A to 100 n c. c. of solvent 

 B, was designated as an "n per cent A (100 n) per cent B mixture." 

 This method of preparing mixed solvents was deemed preferable to the more 

 common method of diluting n c. c. of solvent A to 100 c. c. with solvent B. 

 In the latter case it is always necessary to state which solvent is used as 

 diluent, and the mixture must always be allowed to cool down to the tempera- 

 ture of the unmixed solvents before the final dilution to the mark on the 

 measuring-flask can be effected. 



CONDUCTIVITY. 

 APPARATUS. 



In making conductivity measurements, the usual Kohlrausch method, 

 with Wheatstone bridge, induction coil, and telephone receiver, was used. 

 The bridge- wire was of "manganin." The resistance coils were calibrated to 

 within 0.04 per cent. 



The conductivity cells were of the type devised by Jones and Bingham 1 

 for use with volatile solvents, which, like acetone, attack rubber and wax. 

 They differ from the simple Arrhenius cells in that the cup is closed by a 

 ground-glass stopper, into which are sealed with glass the tubes that carry the 

 electrodes. 



The electrodes were carefully cleansed with chromic acid and covered with 

 platinum black, by electrolyzing a dilute solution of platinic chloride. All 

 absorbed chlorine was removed with sodium hydroxide, and the plates were 

 washed with dilute hydrochloric acid and distilled water, dried, and heated to 

 redness in the flame of a blast-lamp. Electrodes thus treated gave a good 

 tone minimum, did not appreciably absorb salts from their solutions, and 

 showed no tendency to cause the rapid oxidation of alcohol to acetic acid. 

 When not in use the cells were filled with distilled water. Solutions were 

 never allowed to stand in them longer than was necessary. 



The zero-bath was of the form commonly used in this laboratory. A tin pail 

 was filled with finely crushed ice and water, and the cells were then packed 

 into the ice as tightly as possible. The pail was placed in a larger, indurated 



'Amer. Chem. Journ., 34, 481 (1905). 



