Density comparison method for the measurement of isotopic variations in prepared waters

The falling-drop method of density determination has been modified so that the densities of a standard and a sample water are compared simultaneously. A constant temperature bath that does not vary more than 0.0001°C and an accurate double micropipet are described. The method has sufficient sensitivity and precision to distinguish waters that differ in specific gravity by 0.025 micrograms per ml. The method could be applied to the measurement of small variations in the isotopic composition of prepared waters.