Addition of gases

Gaseous reagents are usually introduced via a glass tube below the surface of a liquid in the reaction flask. To provide extra contact between gas and liquid, the gas can be passed in as small bubbles with the aid of a tube with a fritted glass end. 

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If possible, media should be sterilized in situ. In-line sterilizing filters for routine addition of gases, media, acids or alkalis, defoaming agents, etc., to fermenters should be used where possible. 

One of the major problems in the addition of gases which are not readily soluble in the solution is to minimize loss of the gas. It is desirable to effect a good contact between the gas and the solution, and this is most simply done by passing the gas into the solution through a sintered glass tube, thereby dispersing it into fine bubbles, and at the same time stirring the solution. 

Active surfaces on soil particles are able to adsorb some of the gases with which they come into contact. These surfaces are normally in equilibrium with the contents of the pores that surround them and their adsorbed gas concentrations are therefore representative of the gas concentration in the pores. Soil samples are a particularly convenient medium for collection and transport, but they must be treated with care to avoid losses or additions of gases during transport and storage. 

The Dewar apparatus can be readily adapted to mimic real plant configurations, including agitation, addition of gases, liquids or solids, and systems for heating and cooling. Descriptions of such systems are well-documented in... 

The characteristics of the plasma can also be modified by adding another gas to argon. For instance, an addition of O2 to the plasma is beneficial for the analysis of organic solutions as it prevents the deposition of soot on the interface. The addition of gases with a higher thermal conductivity than argon (such as H2) can be used to enhance sensitivity (by improving the ionization efficiency), reduce and/or eliminate spectroscopic and non-spectroscopic interferences, and reduce mass discrimination. 

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