Application of Coulometric Titration for the Certification of Primary Reference Materials of Pure Substances

In this article, the block scheme and metrological characteristics of the State primary standard of the mass (molar) fraction and mass (molar) concentration of the component in the liquid and solid substances and materials based on coulometric titration GET 176-2010 are given. Primary reference materials certified by coulometric titration in the Ural Scientific and Research Institute for Metrology include eight certified reference materials (CRMs) of pure solid substances (mostly salts of sodium or potassium) and one hydrochloric acid solution CRM. The metrological characteristics of these reference materials and the scheme of their application in titrimetric analysis are shown. The expanded uncertainty of the certified value (mass fraction for the solid substances or molar concentration for the solution) is in the range from 0.018% to 0.05%. Information about two primary reference materials of high purity iron and lead nitrate certified by controlled-potential coulometry with expanded uncertainty from 0.04% to 0.07% is also given.