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at their boiling point AHb/AH°i s between 0.75 and 0.79. For hydrogen bonded liquids this ratio is larger, the magnitude of the ratio increasing as the strength of hydrogen bonding increases. The values indicate that the lower alcohols show stronger hydrogen bonding than water which is in conformity with the findings of Pauling.3Table I indicates that AHa/AH°v alues for alcohols decrease with increasing chain length; while the reverse is true for organic acids. Because an increase in chain length results in an increase in the boiling point of a given homologous series a de-(3) L. Pauling, "The Nature of the Chemical Bond," Cornell Press, Ithaca, N. Y" 1948, p. 304. crease in bond strength at the boiling point would be expected. The results for acids suggest a change in type of bonding with increasing chain length. Both acids and alcohols are strongly hydrogen bonded; however, acids show a great tendency to form dimers. It appears, therefore, that with increasing chain length the acids decrease in dimeric hydrogen bonding and increase in infinitic lattice hydrogen bonding.The theory presented above for the heat of vaporization of the liquid-vapor surface layer should prove of value to workers investigating surface phenomena. It also should be useful in differentiating types of bonding.

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