A semitheoretical equation

log P=A- (B/TN) (I)

and an empiricallymodified Antoine equation

logP= A-(B/T-C)+DTM(Ⅱ)

are proposed for cor- relating liquid pressure with temperature. These two equations together with the regular Antoine equation

logP=A-(B/T-C) (Ⅲ)

and the equation

logP = A-(B/TN) + CTM (Ⅳ)

proposed by Thodos et al.

have been used to fit the high-pressure data of 1631 points for 68 substances

published since 1962 through 1982. The results show that all these four equations are applicable up to the critical points. The grand average deviations between the calculated and experimental values are about 0.4% for the three-constant equations ( I ) and (Ⅲ)

and about 0.2% for the four-constant equations(Ⅱ) and (Ⅳ). The effect of adopting different values of M in equations (Ⅱ) and (IV) is not significant

and M=l is therefore suggested. The values obtained for the parameters of equations ( I ) and ( Ⅱ) are presented for the 68 substances. The three-constant equations ( I ) and (Ⅲ) are recommended for general use

equation (I) being more convenient than (Ⅲ) for mathematical treatment.