Capacitance is used as a measuring technique for non-conductive liquids where all other measurement techniques are inapplicable. The indicated level is proportional to the dielectric constant of the liquid, therefore the technique cannot be used reliably where the liquid blend or other properties (like temperature) are changing.
Conductivity is used as a purity measurement technique in industrial water generation; in general, the lower the conductivity the higher the purity.
There is no relationship between 1 and 2 in this context.
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