How to prepare standard gas?
1. Air dilution
The standard gas obtained by air dilution method is generally of high concentration, so it is not suitable to be used as standard gas directly. Instead, it is used as raw gas and prepared into the standard gas with required concentration through appropriate methods.
2. Gas storage
Standard gases, no matter how they are produced, are usually collected and stored in appropriate containers. Manufacturers typically press them into cylinders or aluminum bottles and dilute them with clean gas to a concentration for sale as merchandise. However, it should be noted that the stored gas cannot interact with the container chemically, nor can it escape through the walls or gaps of the container. Therefore, the container containing the gas must be treated to prevent the cylinder from reacting with the gas.
3. Occurrence of gases
Due to the different physical and chemical properties of various substances, they exist in different forms. Therefore, the methods of obtaining standard gases are also different. For the more volatile substances existing in the liquid state, the volatilization of the liquid can be used to prepare. It can also be made by chemical reactions.
Gases produced by the latter method often contain impurities, which must be removed by an appropriate method before being stored in an appropriate container for concentration determination.