An automatic boiling temperature control system for the measurement of both isothermal and isobaric vapor liquid equilibrium data.(T-P-x-y)by dynamic method is presented in this paper

along with the principle of temperature control and total pressure measurement. The absolute pressure control in isobaric VLE measurement can reach the precision of ± 0.02mmHg

and in isothermal VLE data measurement

the precision of the constant temperature control is within ± 0.002℃. The total pressure P is determined by using an ebul-liometer to measure the boiling point of pure water which is then converted to the total pressure. The schematic diagram of the system and the experimental procedure are given in detail. Using this automatic control system

isothermal VLE data of methanol (1)-1

2-dichloroethane (2) at 50.00℃ and 60.00℃ were measured

and both of the data sets passed the point-to-point thermodynamic consistency test. The system has the advantages of accuracy

simplicity and rapidity in isothermal VLE data measurement

and in general

a data point can be determined in about 5 to 10 minutes.