22 CONDUCTIVITY AND VISCOSITY IN MIXED SOLVENTS. 



He thinks that the cause of the minimum in viscosity is more deep-seated 

 than Wagner supposed, and attributes it to "some change in molecular aggre- 

 gation or dissociation." 



Blanchard l found that the addition of 1 equivalent of ammonia for 

 1 equivalent of silver, and the addition of 4 equivalents of ammonia for 

 1 equivalent of copper and zinc in aqueous solutions of their salts, very 

 greatly decreases the viscosity. He reasons that this can not be due to 

 increased ionization, and therefore rejects the electrostriction theory and 

 proposes a hydrate theory. He says that if the positive ion consists 

 solely of a metallic atom bearing an electric charge, combination with 

 ammonia molecules can not decrease its mass or readily increase its sym- 

 metry, so as to reduce the viscosity. The only explanation seems to 

 be that the ions in solution are hydrated. The hydrate water is replaced 

 by ammonia, which forms with the ion a more stable complex and one of 

 smaller mass, or greater symmetry, or both. He believes that this theory 

 also accounts for negative viscosity and for the effect of pressure on viscos- 

 ity. Evidently, this is the same conclusion as that reached by Kohlrausch 

 in his hypothesis of ionic spheres, but by a somewhat different method of 

 approach. 



Blanchard added small amounts of water to alcoholic solutions of sodium 

 hydroxide, and found the viscosity smaller than would be expected from a 

 study of the pure solvents. This is due, as he thinks, to the formation of a 

 complex between the alkali, water, and alcohol, which is, however, smaller 

 or more symmetrical than the alcohol-water complex originally present. 

 Mixtures of alcohol and water give a maximum in viscosity. Blanchard 

 finds that cupric chloride increases this effect. He further applies this 

 theory to the work of Jones and Lindsay, 2 on conductivity. 



The existence of hydrates, or solvates (in the case of non-aqueous solvents) 

 in one form or another is an old conception. Poisseuille 3 first suggested it in 

 working with alcohol and water. Graham * confirmed and extended Pois- 

 seuille's work. Wijkander 5 supposed that acetic acid forms a hydrate with 

 water, C 2 H 4 02 . H 2 0, which would account for abnormal viscosity. The 

 changes due to temperature he attributed to dissociation changes in the 

 liquid. Thorpe and Rodger 6 and Traube a also assume the presence of 

 hydrates. 



Recently, Varenne and Godefroy 7 have found evidence from viscosity curves 

 for the existence of various hydrates in mixtures of water with methyl and 

 ethyl alcohols and acetone. These are shown in table 6. 



'Journ. Amer. Chem. Soc., 26, 1315 6 Wied. Beibl., 8, 3 (1879). 



(1904). "Loc. cit. 



'Arner. Chem. Journ., 28, 329 (1902). 7 Compt. rend., 137, 992 (1903); 138, 



3 Loc. cit. 990 (1904). 



4 Phil. Trans., 151, 373 (1861). 



