ISO 5281:1980

Specifies pyknometer and hydrometer methods. The principle of the pyknometer method bases on weighing an empty pyknometer, then filled with water and, finally, filled with the product under test at known temperatures. Calculation of the density from the values obtained applying certain corrections given in tables. The hydrometer method bases on the immersion of a hydrometer in the product under test and recording the hydrometer scale reading and the temperature. Calculation of the density from the values obtained after applying a correction to be obtained from the calibration certificate.