CHAPTER IV. 



THE CONDUCTIVITY AND VISCOSITY OF SOLUTIONS OF POTASSIUM 



IODIDE AND SODIUM IODIDE IN MIXTURES OF ETHYL 



ALCOHOL AND WATER. 



BY E. P. WIGHTMAN, P. B. DAVIS, AND A. HOLMES. 



A brief review of the conductivity and viscosity work in non-aqueous 

 and mixed solvents, during the past twelve years, is contained in the 

 last chapter of this monograph. 1 All discussion of this work can, 

 therefore, be omitted here. 



EXPERIMENTAL. 

 PURE ANHYDROUS ALCOHOL. 



Pure anhydrous alcohol was obtained in the following manner : The 

 ordinary 95 per cent ethyl alcohol was heated for three days with lime 

 in a copper vessel connected with 

 a reflux condenser. A cooling coil 

 in the neck of the vessel brought 

 about rapid condensation, thus 

 acting as a safety device, so that 

 there was no danger in keeping 

 the alcohol constantly heated 

 during the day without close at- 

 tention. 



In distilling the alcohol, a block- 

 tin condenser connected with the 

 copper vessel by means of a 

 ground-brass joint (see fig. 29) was 

 used. In this way the ordinary 



cork stopper was avoided, and FlGS 2 9 and so. 



the alcohol vapor came in contact 



only with a metal surface before being condensed. The distillate was 

 received into large (glass-stoppered) Jena glass bottles. 



Specific-gravity determinations showed this to contain from 0.1 per 

 cent to 0.07 per cent of water. It was, therefore, heated a second time 

 for three or four days with fresh lime and then redistilled. The dis- 

 tillate obtained in this manner had a specific gravity from about 0.78511 

 to 0.78516, usually nearer the former value, which corresponds|to a 

 percentage of 99.98 per cent alcohol. 



SPECIFIC-GRAVITY DETERMINATIONS. 



Special care was taken in the determination of densities. Two 

 pycnometers (fig. 30), very nearly alike, were used in the case of 



80 



1 See also Carnegie Inst. Wash. Pubs. Nos. 80 and 180. 



