Because Accuracy Matters: Determining Ethanol Concentration With Density Meters

By Siegfried Hold, Christine Bachler, and Nicholas Groseclose, Anton Paar

To determine ethanol concentration with a density meter, a closer look at the specifications of the instrument is required: The more precise the measuring temperature control, the more accurate the density values and therefore the ethanol concentration. If, for example, a high accuracy of ± 0.01 % v/v is required for the ethanol concentration, the resulting measuring temperature has to be kept constant ± 0.01 °C.

Density: A function of temperature
Density is defined as mass per volume. As the volume of a substance changes with temperature, density is also temperature dependent. In terms of a density meter, this means that precise temperature control is crucial to determining correct density values. Depending on the liquid (or, more specifically, on the liquid’s coefficient of expansion) the measuring temperature has to be stable within a certain range to yield the required density accuracy.