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Osmomat 010

Measurement Method

For the determination of the molar mass, the OSMOMAT 010 has to be calibrated first with the pure solvent and then with a solution with known molal concentration. It is then possible to adjust the zero point of the solvent with the range of -5ºC to 10ºC. The cell constant can be obtained from the calibration measurement, which then is used in the determination of the molar mass calculation.

For the sample measurement, solutions of concentrations of about 5 to 140 g/kg solvent will be prepared depending on the expected molecular weight. For the determination of molar masses below 1000 g/mol, a single point measurement is normally sufficient. Nonpolar substances may behave in a non-linear fashion in respect to the ratio measured value/concentrations in the range of low molecular weights and at least 3 solutions with graded concentrations should be measured.

The values obtained in this way have to be treated by means of linear regression analysis.

The total osmolality of aqueous solutions is determined by comparative measurements of the freezing points of pure water and of solutions. Water has a freezing point of 0ºC, a solution with saline concentration of 1 Osmol/kg has a freezing point of -1.858ºC.