Effects of Nonelectrolytes on the Temperature of the Maximum Density of Water. I. Alcohols

The effects of various kinds of alcohol on the temperature of the maximum density of water were observed. The results revealed are as follows : 1) The change in the temperature of the maximum density due to alcohols, ΔT, is not proportional to the solute concentration, disobeying Despretz’s rule and in contrast with ordinary electrolytes. 2) The ΔT for univalent aliphatic alcohols at low concentrations is generally positive; that for tert-butyl alcohol is the largest. The ΔT is likely to become high as the number of carbon atoms and the degree of branching in alkyl radicals increase. 3) The elevation of the temperature of the maximum density due to the interaction of alcohol and water, ΔT′, depends upon the weakness of the cohesion of alcohol and the strength of the hydration of the hydrophilic molecules. 4) As the concentration of alcohol increases, there occurs a lowering of ΔT as a result of interaction between the solute molecules themselves. Similar interactions are seen between different alcohol molecules in ternary systems, but can not be seen between alcohol and electrolytic ions, where the solutes behave independently of each other. In the last case, the additivity of ΔT is realized fairly well.