Abstract: A calibration device having a thermally insulated storage receptacle for a liquid to be analyzed. The liquid is converted to a vapor form by passing a carrier gas through the liquid to be analyzed whereby the carrier gas is saturated with the liquid. The partial pressure of the liquid vapor in the gas is the function of the temperature of the liquid and the pressure of the saturated carrier gas. The saturated carrier gas is applied to the sample inlet of a vapor phase analyzer by a sample transport line that is maintained above the dew point of the saturated carrier gas. Since the concentration of the calibration liquid in the carrier gas can be precisely calculated by measuring the liquid temperature and the pressure of the saturated carrier gas, the response of the analyzer can be calibrated to this known concentration while maintaining the liquid to be analyzed in a liquid state.