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National Standard of amount of substance

Name of the standard: National Standard of amount of substance

Code designation: ECM 330-1/21-067

Year of promulgation: 2021

Department: dpt. 6016 CMI, RI Brno

Guarantor: Mgr. Matilda Roziková, Ph.D.

The number of CMC lines provided: 1

The main unit of amount of substance is mole, the sixth basic unit of the SI system. The measurement of amount of substance is one of the most widespread measurements, although it is relatively less accurate compared to the physical ones. The relative uncertainties of measurements come up to the range from 10-5 to 10-6 moles. The measurements of amount of substance are required not only in the chemical industry, but also in other important areas such as geology, healthcare, metallurgy and food industry. The traceability of the state standard of amount of substance is realized through units of electrical resistance and weight.

Coulometry as a primary method for the determination of amount of substance has an irreplaceable role for the metrological institutes on the international scale. It is used for the certification of the pure substances – primary reference materials with combined uncertainty of the main component below 0.01 %, or solution of pure substances without interfering matrix. It is used for the realization and transfer of amount of substance unit through primary certified reference materials.

In the years 2014–2021, Czech metrology institute built the primary standard for the determination of amount of substance on the base of high precision coulometric equipment, that was proclaimed as the state standard of amount of substance.

The main goal of the state standard primary measurements is certification of primary reference materials of amount of substance with the direct determination of main component (substance purity). These primary reference materials can be subsequently used for the traceability of the measurements in various chemical experiments.

The National Standard standard of amount of substance consists of the following parts:

Precise current source CS 8011 A
Indication unit IU 7011 A
Ventilation unit VU 9018 A
Piston burette Titronic® 500
Magnetic stirrer 
Weight CP 225D-OCE
Weight PR 5003 comparator
Digital capacitive hygrometer with thermometer D3121
Digital pressure gauge DPI 141
Laboratory furnace type 003 LP
Computer and measuring software
Electrochemical chamber

Basic metrological characteristics:

Amount of substance of H+ expressed as hydrochloride acid:

Range of amount of substance:   0.09 - 0.11

Extended uncertainty U (k = 2):   5.3. 10-6


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