This paper gives experimental critical temperatures and pressures of 10 n-alkylbenzenes C 6 H 5 C n H 2n+1 with the number of carbons in the side chain n ) 1, 2, 4, 5, 6, 7, 8, 10, 11, and 13. n-Alkylbenzenes that are heavier than butylbenzene are thermally unstable at their critical points. The method of pulse heating of a wire probe placed into the liquid under study has been used. Residence times are from (0.01 to 1) ms. Equations for the correlation of the critical temperatures and pressures of n-alkylbenzenes with the number of carbon atoms in the side chain, molar mass, and normal boiling point have been obtained. The experimental critical constants of alkylbenzenes have been compared with the values calculated by the methods of Lydersen, Joback and Reid, and Constantinou and Gani.

The critical temperatures and pressures of phthalates with the straight side alkyl chains C 6 H 4 -1,2-[COO(CH 2 ) n H] 2 (n is from 1 to 11) as well as bis(2-ethylhexyl) phthalate have been measured. No literature data are available for the critical properties of phthalates. Since phthalates decompose at temperatures well below their critical temperatures, the method of pulse heating of a wire probe immersed into the liquid under study has been used. The method minimizes the effect of thermal decomposition because residence times are only from (0.035 to 1) ms. The experimental critical properties of phthalates have been compared with the values calculated using the group-contribution methods by Constantinou and Gani and Marrero and Gani.

The critical temperatures and pressures of nine saturated straight-chain dicarboxylic acids HOOC(CH2) n COOH with n = 2, 3, 4, 5, 6, 7, 8, 10, and 12 have been measured. All of the acids investigated are thermally unstable at their critical points. The method of pulse heating of a wire probe immersed in the liquid under study has been used. Residence times are from (0.01 to 1) ms. The experimental critical properties of dicarboxylic acids have been compared with the values calculated by the group-contribution methods of Ambrose, Joback, and Reid, Constantinou and Gani, and Marrero and Gani.