Families of compressed gases

Compressed and liquefied gases are often described according to loosely knit families. Such designations can be somewhat arbitrary and are usually based on either a common source, a similar use, or a related chemical structure. 

Part III of this book is comprised of monographs on individual gases and indicates predominant chemical characteristics 

But these two gases have a great many other uses as well. Oxygen is used to produce stronger steels less expensively. It is also used together with acetylene and other fuel gases such as propane to weld or cut steel in fabricating structures and machinery. It is used in medical treatment and respiratory therapy. 

Hydrogen also occurs minutely in the atmosphere, as do a large variety of trace constituents, small amounts of carbon dioxide, and large amounts of water vapor. 

Carbon dioxide fire extinguishers are commonly used for protection against chemical and electrical fires, while carbon dioxide dissolved under pressure makes the sparkle in 

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Most polymer products are offered for recycling in the form of mixed plastic waste (MPW). Compressed gases as solvents may offer advantages compared with liquid solvents in the necessary separations (e.g., to collect families of polymers out of MPW) because such solvents are easy to recover and, furthermore, they make it possible to use pressure as an additional separation parameter or to remove the organic additives of the polymers. Finally, MPW may be added as a polymer solution in a compressed gas to a feed of a Naphtha cracker, and thus be recycled to base chemicals. 

A few hydrocarbon derivatives from the alkyl-halide family are 2.2 nonflammable compressed gases. This illustrates the wide range of hazards of the alkyl halides as a group. Some are flammable, some are toxic, and some are nonflammable and nontoxic. They can still act as asphyxiants and displace the oxygen in the air. It is important to remember that the primary hazard of the alkyl halides is toxicity. Some of them are also flammable therefore, all must be assumed to be toxic and flammable until the individual chemical is researched and the actual hazards are determined. It is interesting to note that while the DOT lists tetrafluoromethane as a nonflammable, nonpoisonous gas, the Condensed Chemical Dictionary lists the compound as toxic by inhalation. The NIOSH Pocket Guide to Chemical Hazards does not list the compound. The best source of information about this compound and others may be the MSDS (material safety data sheet). Examples of nonflammable Class 2.2 alkyl halides are tetrafluoromethane and trifluoromethane. 

This chapter provides an introduction to compressed gases. Included are descriptions of the various groupings and families into which gases are categorized, as well as information concerning standard units of measurement. This is useful background information especially to anyone unfamiliar with gases. 

Part II of this book provides monographs on individual gases and indicates predominant chemical characteristics for each gas. However, it is important to remember that any particular gas may exhibit several characteristics to varying extents. The following paragraphs describe some typical families by which compressed gases may be categorized. 

Many valve outlet and inlet connections have been standardized by CGA for the different families of gases to prevent the interchange of regulator equipment between gases that are not compatible. These standardized connections have been adopted by the American National Standards Institute (ANSI) and CSA. Refer to Chapter 9 and ANSI/CGA V-1, American National, Compressed Gas Association Standard for Compressed Gas Cylinder Valve Outlet and Inlet Connections [6]. 

Another extensive family is that of refrigerant gases. A refrigerant gas is one that liquefies easily under pressure, for it works by being mechanically compressed into a liquid. In this state, it absorbs large amounts of heat as it circulates in cooling coils, eventually vaporizing back into a gas. 

Fluids in the hydrocarbon group represent the bulk of pipeline utilization, with natural gas being the predominant user within that family. The increased use of carbon dioxide for oil field stimulation has created a dramatic growth in pipeline construction for that commodity. Other compressed gases distributed by pipeline include ammonia, chlorine, nitrogen, and oxygen. 

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