Method for measuring the ionic activities in water with a differential pressure transducers

Abstract

An apparatus and method that gives very accurate measurements which allow one to determine the values of ionic activities of aqueous electrolyte solutions. To obtain these accurate measurements, moderately accurate measurements of vapor pressure differences between pure water (or a reference liquid) and the aqueous electrolytes is first obtained. A container with a known solution of nonvolatile electrolyte in water, i.e., a solution of known composition, is connected to one side of a differential pressure transducer, the other side of which is connected to a second container with a deionized double distilled water. Next, the gas in the containers and dissolved in liquids is evacuated by using a mechanical pump and the containers are immersed in a temperature controlled medium. At this point in time, the differential pressure transducer measures the difference in pressure. This reading may be used to obtain the vapor pressure of the solution and then determine corresponding ionic activities of the electrolyte in the solution.

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