Mass flow meter
The mass flow meter does not measure the volume per unit time (e.g., cubic meters per second) passing through the device; it measures the mass per unit time (e.g., kilograms per second) flowing through the device. Volumetric flow rate is the mass flow rate divided by the fluid density. If the density is constant, then the relationship is simple. If the fluid has varying density, then the relationship is not simple. The density of the fluid may change with temperature, pressure, or composition, for example. The fluid may also be a combination of phases such as a fluid with entrained bubbles.
Actual density can be determined due to dependency of sound velocity on the controlled liquid concentration.
Methanol (data page)
Here is a similar formula from the 67th edition of the CRC handbook. Note that the form of this formula as given is a fit to the Clausius–Clapeyron equation, which is a good theoretical starting point for calculating saturation vapor pressures:
Data obtained from "Lange's Handbook of Chemistry", 10th ed. and "CRC Handbook of Chemistry and Physics" 44th ed. The annotation, "d a"°C/"b"°C, indicates density of solution at temperature "a" divided by density of pure water at temperature "b" known as specific gravity. When temperature "b" is 4 °C, density of water is 0.999972 g/mL.Except where noted otherwise, data relate to standard ambient temperature and pressure.