Nitric Acid Solutions as a Basis for Reference Materials of Specific Electrical Conductivity of Liquids

   Metrological support of conductometric liquid analyzers in accordance with the State Verification Schedule for Means of Measuring Specific Conductivity of Liquids requires the use of certified reference materials. Analysis of information on certified reference materials in the Federal Information Fund for Ensuring the Uniformity of Measurements revealed the absence of reference materials of specific electrical conductivity of certified liquids with certified values over 20 S/m. It was necessary to determine the source material for developing test samples: the authors hypothesized that nitric acid solutions can be used as the basis for reference materials of specific electrical conductivity of liquids. The article presents the materials of the study of the metrological characteristics of aqueous solutions of nitric acid for their further use as a initial material in the development of reference materials used to transfer the unit of specific electrical conductivity of liquids to conductometric liquid analyzers. The result was the development of test samples of nitric acid solutions with a nominal value of specific electrical conductivity of 35, 50, 85 S/m and the subsequent assessment of their certified value, and the determination of the confidence limits of the relative error. The studied nitric acid solutions can be used to transfer the unit of specific electrical conductivity of liquids from the working standard of the 1^st and 2^nd categories to measuring instruments using the direct measurement method. The research materials can form the basis for future improvement of GET 132-2018 in terms of expanding the measurement range from 50 to 100 S/m. The article is addressed to metrologists engaged in verification, calibration and testing for approval of types of conductometric liquid analyzers. The published review of literary data may be useful for specialists of specialized institutes.

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