1. A vapor pressure analyzer to determine the vapor pressure of single or multi component liquids comprising of an inlet conduit, a filter, a heating/cooling means to condition the single or multi component liquid, an upstream aeration measurement means to establish an aeration reference of the liquid, a capillary tubing pressure reduction means to decrease the pressure of the liquid smoothly to its vapor pressure oriented in a horizontal position or a pressure reducing valve which does not create pressure recovery nor a vena contracta, such vena contracta resulting in some pressure recovery and erroneous data, a downstream aeration measurement means that detects the minimum change in aeration compared to the upstream aeration measurement resulting from the pressure having reached the vapor pressure of the lightest component of the sample, a pressure measurement means to measure the actual vapor pressure at the point where the liquid starts to flash or effervesce, a temperature measurement means at the same location as the pressure measurement means, instrumentation and control means to control the liquid flow and therefore the pressure drop across the pressure reduction means at the desired condition that will result in the vapor pressure occurring at the point where the pressure measurement means is located, a pump to increase the liquid pressure back to system pressure to return the liquid back to the system at a point downstream of an extraction point, instrumentation means to process the difference in aeration between the sample upstream and downstream of the pressure reduction means, and flow tubing interconnecting the above mentioned devices.

2. A vapor pressure analyzer according to claim 1 containing instrument and control means to control the flow of the liquid admitted to the analyzer such that the pressure drop through the pressure reduction means is the minimum required to flash the fraction of the mixture having the highest vapor pressure as indicated by the minimum change in aeration that can be attributed to initial flashing or formation of bubbles in the sample as indicated by the difference between the upstream and downstream aeration measurement means.

3. A vapor pressure analyzer according to claim 1 containing downstream aeration measurement means such that the vapor pressure is obtained when the downstream aeration value reaches some pre-determined set point aeration value at the given temperature without having to compare with the upstream aeration measurement.

4. A vapor pressure analyzer according to claim 1 containing a capillary tubing pressure reduction means or a pressure reducing valve such that the turbulence and liquid shear created as the liquid passes through the pressure reduction means promote bubble formation or flashing at the actual vapor pressure of the liquid.

5. A vapor pressure analyzer to determine the vapor pressure of single or multi component liquids comprising of an inlet conduit, a filter, a heating/cooling means to condition the single or multi component liquid, an upstream density measurement means to establish density reference of the liquid, a capillary tubing pressure reduction means to decrease the pressure of the liquid smoothly for pressure reduction and oriented in a horizontal position or a pressure reducing valve which does not create pressure recovery nor a vena contracta, such vena contracta resulting in some pressure recovery and erroneous data, a downstream density measurement means that detects the minimum change in density compared to the upstream density measurement resulting from the pressure having reached the vapor pressure of the lightest component of the sample, a pressure measurement means to measure the actual vapor pressure at the point where the liquid starts to flash or effervesce, a temperature measurement means at the same location as the pressure measurement means, instrumentation and control means to control the liquid flow and therefore the pressure drop across the pressure reduction means at the desired condition that will result in the vapor pressure occurring at the point where the pressure measurement means is located, a pump to increase the sample pressure back to system pressure to return the liquid back to the system at a point downstream of an extraction point, instrumentation means to process the difference in density between the sample upstream and downstream of the pressure reduction means, and flow tubing interconnecting the above mentioned devices.

6. A vapor pressure analyzer according to claim 5 containing instrument and control means to control the flow of the sample admitted to the analyzer such that the pressure drop through the pressure reduction means is the minimum required to flash the fraction of the mixture having the highest vapor pressure as indicated by the minimum change in density that can be attributed to initial flashing or formation of bubbles in the sample and not merely to change in density caused by expansion of liquid due to drop in pressure.

7. A vapor pressure analyzer according to claim 5 containing downstream density measurement means such that the vapor pressure is obtained when the downstream density value reaches some pre-determined set point density value at the given temperature without having to compare with the upstream density measurement.

8. A vapor pressure analyzer according to claim 5 containing a capillary tubing pressure reduction means or a pressure reducing valve such that the turbulence and liquid shear created as the sample passes through the pressure reduction means promote bubble formation or flashing at the actual vapor pressure of the liquid.