A typical vapor phase osmometer consists of: (1) two thermistors, one with a polymer-solvent solution droplet adhered to it and another with a pure solvent droplet adhered to it; (2) a thermostatted chamber with an interior saturated with solvent vapor; (3) a liquid solvent vessel in the chamber; and (4) an electric circuit to measure the bridge output imbalance difference between the two thermistors. The voltage difference is an accurate way of measuring the temperature difference between the two thermistors, which is a consequence of solvent vapor condensing on the solution droplet (the solution droplet has a lower vapor pressure than the solvent).