Abstract
A standard reference gas is usually supplied in a high pressure gas cylinder. The supply system for the standard reference gases is based on traceability as follows:
1) The primary standard gases of pure gases are settled by the National Chemical Laboratory for Industry, and the primary standard gas mixtures are prepared by Chemical Standards Center.
2) On the other hand, when the commercial utility gases are made by the gas manufacturers, are inspected by Chemical Standards Center using the secondary standard reference gases.
The primary standard gases are prepared by the gravimetric method using a ultra high precision semi-automatic balance.
Stability of concentration of gas mixtures in the high pressure gas cylinder were pointed out how to maintain it and were investigated it.
Moreover, it is described how to dissolve some problems on the standard reference gas mixtures in the future.
