The influence of temperature on surface tension

The influence of temperature on surface tension. An immense number of investigations have been carried out on this subject, but clear conclusions as to the meaning of the results in terms of molecules are as yet difficult to reach. Surface tension, or the free energy per unit area 

Eotvos having previously given a rather less accurate equation in which the constant 6° was not subtracted from the critical temperature. Mv is the molecular volume and Tc the critical temperature. 

Eotvos deduced his equation theoretically from considerations of corresponding states of liquids of similar molecular constitution, which are rather difficult to follow. The central point of the theory is, however, that surfaces should be compared on the basis of the number of molecules per unit area, which is, if the molecules are similar in shape and symmetrically packed, proportional to (Jfv)1. 

The constant k was found, for a great number of normal liquids, to have a value close to the mean value, 2 12. Some liquids, notably water and others containing hydroxyl groups, gave a decidedly lower value for h, the temperature coefficient of a quantity called the molecular 

These abnormally low values were supposed to be due to association of the molecules of the liquid, M being higher than calculated from the formula. Assuming that the whole change in the number of molecules in the surface is due to simple association of molecules of molecular weight M to molecules of weight Mv Ramsay and Shields calculated the degree of association thus 

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