National Physical Laboratory

Gravimetric methods for the preparation of standard gas mixtures.

Milton, M J T, Vargha, G M, Brown, A S
Metrologia, 2011, 48, (5), R1-R9
NPL Doc. Ref:
PDB: 6070 | DDB: 4447
Document Type:
Periodical article

Note: An asterisk after an author's name indicates a non-NPL author.


The most widely-used method for the preparation of primary standard gas mixtures involves weighing the individual components into a cylinder usually at high pressure. We present a mathematical description of the method and its uncertainties. We use this to demonstrate how strategies for serial dilution can be identified that minimise the uncertainty in the final mixture and show how they can be implemented practically. We review published reports of high accuracy gravimetry and give examples of uncertainties in the composition of standards approaching 1 part-per-million in the best cases and in the range 100 to 1000 parts-per-million more typically.

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