UCRL-7167 which we used was the necessity for a general correspondence of the maximum and minimum of the deviation curve with those for similar substances. Then, since only two data are necessary among items 2, 3, and 4, the choice of either T or P fixed the other. The considerations involved in the choices c c of T and P will be discussed below in connection with the specific comc c ^ pounds involved. B. SHAPE OF CURVES For the generalized comparison of the deviation curves, the temperature range between the boiling point and the critical point was normalized on a 1/T basis and expressed as percent, where