Development of a reference material for the composition of 0.1 m potassium dichromate solution. Certified reference material GSO 10992-2017

This paper describes key stages in the development and investigation of a high-precision certified reference material (CRM) for the composition of potassium dichromate solution. The proposed reference material (RM) exhibits metrological traceability to the units of the International System of Units (SI). Not requiring additional preparation before use, the CRM is convenient for use as a titrant in redox titration. The metrological characteristics of the developed CRM were determined by the direct primary method of coulomet-ric titration using the State Primary Standard GET 176. The interval of permissible certified values of the molar concentration of potassium dichromate in the CRM under study is found to vary from 0.098 mol/dm 3 to 0.102 mol/ dm 3 . The relative expanded uncertainty (k = 2) of the certified value ofpotassium dichromate molar concentration is calculated to be 0.024 %, with relative standard uncertainties caused by long-term and short-term instability each being equal to 0.0044 %. The shelf life of the developed CRM is found to be 1 year, provided that storage conditions are ensured. A procedure for measuring the molar concentration ofpotassium dichromate is described, along with the equipment used. A comprehensive uncertainty budget for the measurements is assembled. The developed CRM is included into the State Register of Certified Reference Materials under the number GSO 10992-2017. The CRM can be used for transferring the mass (molar) concentration unit of a component to RMs and chemical reagents via oxidation-reduction reactions; the verification and calibration of measuring instruments (MI), as well as control of metrological characteristics during MI trials including type approval; MI graduation; validation of measurement procedures; control of measurement results when determining the mass (molar) fraction and mass (molar) concentration of components in liquid and solid substances and materials.