Density is a popular choice to measure a physical property of a binary solution in order to determine the individual concentrations. When a third component is added to the mix, another physical property measurement, such as refractive index or sound velocity, is required to obtain all three concentration values.

Anton Paar Feb 2018 image
When considering which physical properties to measure for a particular ternary liquid, it is important to find ones that react differently to concentration changes.
For applications which have not previously been developed, it is necessary to make laboratory measurements using samples with various known concentrations that cover the entire possible range. It is best to make as many physical measurements as possible since it is difficult to know in advance which will be the most suitable.
Some ternary samples with established concentration determination methods are listed in a document released from Anton Paar, now available from download from this link.
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