The following methods are usually used by Linde for the filling of high quality gas mixtures in cylinders:
In gravimetric preparation state-of-the-art high-sensitivity, high-load balances are employed. This produces a direct correlation between the weighed gases and the basic unit “kg” or “mole”. If necessary, calibration gas mixtures in the ppm range can be prepared gravimetrically by using suitable “pre-mixtures”.
This preparation method is a combination method. It is usually employed when minute quantities of calibration components are added to a balance gas, e.g. by means of gas-tight syringes.
In this method the pressure changes after adding of the individual calibration components/balance gas are measured. Precision manometers are used for this.