68 



CONDUCTIVITIES OF ORGANIC ACIDS 



L J 



C 



Since the percentage temperature coefficients of conductivity for 

 substances in alcohol, as well as the coefficient of expansion of the 

 alcohol itself, are so large, it is necessary to have fairly close tempera- 

 ture regulation. This was secured by the combination of a specially 

 devised gas regulator and thermo-regu- 

 lator. These have already been de- 

 scribed 1 in earlier papers. 



In cooperation with Dr. P. B. Davis, 

 of the Chemical Laboratory of the Johns 

 Hopkins University, a new form of con- 

 stant-temperature bath was also de- 

 signed. Its construction can be seen 

 from fig. 22. A full discussion of the 

 form finally adopted will be presented in 

 a paper soon to be published by Jones, 

 Davis, and Putnam. 2 In these baths the 

 temperature ordinarily does not vary 

 more than 0.02 C., which is sufficiently 

 constant for our purpose. With special 

 precautions as to insulation from changes 

 in temperatures, and a further modified 

 form of the thermo-regulator, the varia- 

 tion can be decreased to a few thousandths 

 of a degree. Aside from the better 

 temperature regulation obtained in this 

 new form of thermostat-bath, there are 

 also one or two other advantages derived from its use. The apparatus 

 is of copper which does not rust, and the stirring arrangements and 

 the cooling coil are on the side, and are therefore out of the way. 

 A number of minor improvements were likewise added. 



Solutions were made up in 200 c.c. flasks calibrated for 25, and 

 the conductivity measurements of these solutions were taken at 15, 

 25, and 35. Pipettes were frequently used for measuring purposes 

 because of greater ease in handling. They were carefully calibrated. 

 Corrections for the expansion and contraction of the alcoholic solutions 

 at 35 and 15, respectively, were of course applied to the conductivity 

 measurements. 



The alcohol was prepared by heating ordinary 95 per cent alcohol 

 for several days with fresh, unslaked lime in a copper tank, provided 

 with a ground-brass stopper and reflux condenser, and then distilling 

 through a block-tin condenser. The distillate thus prepared was 

 reheated with fresh lime and again distilled, the first and last portions 



TTT3 



FIG. 22. 



it. phys. Chem., 85, 519 (1913); Journ. Chim. Phys. July 1914. 

 2 See Chapter VI of this monograph. 



