In fire extinguishers

In this sequence the Cl also acts as a catalyst and two molecules are destroyed. It is estimated that before the Cl is finally removed from the atmosphere in 1—2 yr by precipitation, each Cl atom will have destroyed approximately 100,000 molecules (60). The estimated O -depletion potential of some common CFCs, hydrofluorocarbons, HFCs, and hydrochlorofluorocarbons, HCFCs, are presented in Table 10. The O -depletion potential is defined as the ratio of the emission rate of a compound required to produce a steady-state depletion of 1% to the amount of CFC-11 required to produce the 1% depletion. The halons, bromochlorofluorocarbons or bromofluorocarbons that are widely used in fire extinguishers, are also ozone-depleting compounds. Although halon emissions, and thus the atmospheric concentrations, are much lower than the most common CFCs, halons are of concern because they are from three to ten times more destmctive to O, than the CFCs. 

Industrial Applications. Perfluoroacylbenzene sulfonates, used as additives in fire-extinguishing compounds and galvanizing baths have been prepared (88). Perfluoroacylbenzenesulfonate salts prepared by Friedel-Crafts reaction of perfluoroacyl haUdes and benzene, and subsequent sulfonation have been used as surfactants (89). 

An important use of bromine compounds is in the production of flame retardants (qv). These are of the additive-type, which is physically blended into polymers, and the reactive-type, which chemically reacts during the formation of the polymer. Bromine compounds are also used in fire extinguishers. Brominated polymers are used in flame retardant appHcations and bromine-containing epoxy sealants are used in semiconductor devices (see... 

Liquid carbon dioxide is discussed on page 261. Carbon dioxide gas is commonly used for carbonating drinks, in fire extinguishers, for gas-shielding of welding and in shell moulding in foundries. Its physical and toxicological properties are summarized in Tables 8.5, 8.6 and 5.29. 

Production in the USA is 350000 tonnes annually of which 30% is used in baking-powder formulations, 20% in animal feedstuffs, 15% in chemicals manufacture, 11% in pharmaceuticals, 9% in fire extinguishers and the remaiiung 15% in the textile, leather and paper industries and in soaps, detergents and neutralizing agents. 

There are natural sources of brominated hydrocarbons as well as man-made sources, such as the "halons , which are used in fire extinguishers. Reaction 21 is very fast and generates Cl and Br atoms directly the cycle does not require a photolytic step. Although this cycle occurs with high efficiency, it is less important than the chlorine peroxide cycle because of the much smaller concentrations of bromine compounds in the stratosphere-parts per trillion vs. parts per billion for the chlorine compounds. 

The nature of the reactants. Carbon tetrachloride (CC14) does not burn in oxygen, but methane (CH4) burns very well indeed. In fact, CCI4 used to be used in fire extinguishers, while CH4 is the major component of natural gas. This factor is least controllable by the chemist, and so is of least interest here. 

Chloroform is used primarily in the production of chlorodifluoromethane (hydrochlorofluorocarbon-22 or HCFC-22) used as a refrigerant for home air conditioners or large supermarket freezers and in the production of fluoropolymers (CMR 1995). Chloroform has also been used as a solvent, a heat transfer medium in fire extinguishers, an intermediate in the preparation of dyes and pesticides, and other applications highlighted below. Its use as an anesthetic has been largely discontinued. It has limited medical uses in some dental procedures and in the administration of drugs for the treatment of some diseases. 

Uses Manufacture of fluorocarbon refrigerants, fluorocarbon plastics, and propellants solvent for natural products analytical chemistry cleansing agent soil fumigant insecticides preparation of chlorodifluoromethane, methyl fluoride, salicylaldehyde cleaning electronic circuit boards in fire extinguishers. 

Carbon dioxide (CO ) is the 18th most frequently produced chemical in the United States. It has numerous uses, including in refrigeration, in the manufacture of carbonated drinks (e.g., soda pop), in fire extinguishers, in providing an inert atmosphere (unreactive environment), and as a moderator for some types of nuclear reactors. 

Uses. In the manufacture of chlorofluoro-carbons, which in turn are primarily used as refrigerants formerly used widely as a solvent, also as a grain fumigant and in fire extinguishers. Because of toxicity consumer uses have been discontinued and only industrial use remains. 

Applications of ammonium carbonate are similar to those of ammonium bicarbonate. It is used in baking powder in fire extinguishers as mordant in dyeing for washing and defatting wools in tanning in manufacture of rubber products as a smelling salt as a source of ammonia, and as an expectorant. 

Monobasic ammonium phosphate is used in fire extinguishers as a flame retardant for papers, plywoods, and fabrics in haking mixtures and in fermentation process. 

Potassium bicarbonate is used in baking powder and effervescent salts. In medicine, the salt is a gastric antacid and an electrolyte replenisher. It also is dry powder in fire extinguishers. 

In the coal gasification, as well as in the FT process massive amounts of CO are inevitably produced. CO is the main component of the off-gas in the Sulphur recovery plarft (see above) and in the Benfield plant (which scrubs CO2 from the Synthol tailgas). The latter source is the purer of the two. CO is used in fire extinguishers and the production of "dry ice". 

LIQUID CARBON DIOXIDE IS USED IN FIRE EXTINGUISHERS. 

Carbon dioxide is used in beverages and in fire extinguishers. The "bite" of carbonated beverages is due to the mild acidity of C02 solutions (pH 4), which results when approximately 0.3% of the dissolved C02 is converted to carbonic acid (H2C03), a weak diprotic acid (Section 15.11) ... 

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