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2032 nitrogen (us. ice) was also monitored while measuring r for H6 in EPA. The temperature fluctuated /6(l/T) (AH," - A G m o ) / T
where AS," is defined as (molar entropy in - (molar entropy in the standard state.)
AH,II
=
AH," - AH,,,'
(11)
which, through eq 6, reduces to AH,II
=
AH,"
(12)
The enthalpy change is then given, by using either eq 3 and 8 or eq 10 and 12, as
AS,II
=
AH,"/T
(13)
where AS,I1 is defined as (molar entropy in the micelle) - (molar entropy at the cmc). The literature reveals that the entropy of micellization is calculated in one of two ways: either through the use of eq 3 or eq 13. While the latter is more definitive in describing the entropy changes occurring upon micellization, actual data on this phenomenon are scarce, due to the fact that calorimetric AH," values suffer from various uncertainties, especially when the alkyl chain contains more than about ten carbon atom^.^,^ To circumvent this problem, a number of workers derive a AH, according to eq 2, and immediately introduce this term into eq 13. The entropy values thus obtained are (1) K. Shinoda, J . Phys. Chem., to be published. (2) J. Swarbrick and J. Daruwala, ibid., 73, 2627 (1969). (3) P. Molyneux, C. T. Rhodes, and J. Swarbrick, Trans. Faraday Soc., 61, 1043 (1965). (4) D. G. Hall and B. A. Pethica, "Nonionic Surfactants," M. J. Schick, Ed., Marcel Delrker, Inc., New York, N . Y., 1967, Chapter 16. (5) L. Benjamin, J . Phys. Chem., 68, 3575 (1964). Volume 74, h'umber 9 April SO, 1070
