96 Studies on Solution. 



The viscosities of mixtures of formamid with ethyl alcohol as well 

 as those with water show only a slight deviation from the normal 

 values for mixtures, being always somewhat less than the calculated, 

 giving rise to a sagged curve. This has been observed by Merry and 

 Turner, 1 who studied the viscosities of binary mixtures of formamid 

 with methyl and ethyl alcohols and with water. They have shown this 

 deviation to be due to decrease in the association of one or the other 

 components or of both. It is not possible to account for this phenom- 

 enon by the theory of Jones and Veazey, since from this standpoint a 

 maximum in the viscosity curve would be expected. 



The conductivity values for mixtures containing calcium nitrate 

 give evidence of greater variation than the other salts in analogous 

 mixtures. It is seen in table 56 that the maximum in the values for 

 molecular conductivity does not occur in 25 per cent formamid and 75 

 per cent ethyl alcohol mixtures as for the other salts, but the maxima 

 appear in the concentrated formamid mixture and in the concentrated 

 solutions. The conductivity is greater in the 75 per cent to 25 per cent 

 mixture than in the formamid itself. 



The viscosity of the solutions of the four salts studied in these mix- 

 tures are all greater than those of the solvents. The change in the 

 association of the two components is evidently so slight that appar- 

 ently the size of these molecular aggregates is always greater than that 

 of the molecules or ions of the solute. Rubidium and tetraethyl 

 ammonium iodides have about the same effect on the viscosity of these 

 mixtures. Lithium nitrate and calcium nitrate produce a much 

 larger increment in these mixed solvents analogous to that in pure 

 formamid. The actual increase in the viscosity of the mixtures for 

 any one salt becomes greater in passing from the mixture containing 

 the larger percentage of formamid to that containing the larger per- 

 centage of alcohol. 



A few measurements were made on the viscosity of mixtures of 

 formamid and water, the results confirming those obtained by Merry 

 and Turner 2 i. e., the viscosities for these mixtures show a much greater 

 deviation from the law of mixtures than do mixtures of formamid 

 and alcohol, their viscosities being much less than those calculated 

 from averages. Caesium, rubidium, and potassium salts lower the 

 viscosity of water, but increase that of formamid. Therefore a curve 

 for the viscosities of solutions of these salts in formamid-water mixtures 

 would cross that of the solvent. A study of such curves would yield 

 some interesting results and probably furnish a means of determining 

 the validity of the hypothesis of Jones and Veazey, which has been 

 questioned recently. 3 It is hoped that we may be able to take up this 

 problem at some future time. 



Mourn. Chem. Soc., 106, 748 (1914). 2 Joum. Chem. Soc., 106, 748 (1914). 



3 Cf. Bramley: The Study of Binary Mixtures. Journ. Chem. Soc.. 109, 462 (1916). 



