From other chlorinated compounds

A report [64] that phosgene had been evolved when a horticultural dust, containing DDT, (3.6), was mixed with copper(II) oxide chloride was shown to be unfounded [579]. Rather severe conditions (not likely to be encountered in agricultural practice) are necessary in 

Sugar beet, treated with the organochloride pesticides, hexachlorocyclohexane and sodium trichloroethanoate, results in the contamination of the plantation with dust containing residual amounts of the pesticides. The maximum amount of phosgene produced was associated with the maximum u.v. radiation occurring between hours of strong sunlight [834]. 

Four principles for the treatment of phosgene spillages have been investigated [ICIS6]  

9 Reaction (e.g. soda ash, soda lime, methanol, ethylene glycol, triethylamine) 

The addition of any paraffin(ic) material was found to significantly reduce the rate of phosgene evaporation [ICI55]. The addition of a linear-chain paraffin (Cj -C, ) or kerosine (2 parts of solvent to 1 part of liquid phosgene) reduces the rate of evaporation to 20% of that of an untreated pool. The addition of an inert filler (dried sawdust) impregnated with paraffin was found to be as effective as adding the paraffin, but acted also as a filling material. If this is followed by the addition of an excess of hydrated lime (calcium 

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Sanchez, J., M. Sole, and J. Albaiges. 1993. A comparison of distributions of PCB congeners and other chlorinated compounds in fishes from coastal areas and remote lakes. Inter. Jour. Environ. Anal. Chem. 50 269-284. 

Both hexachloroethane and its lipophilic metabolites can distribute to body fat. Only hexachloroethane can be used to confirm compound exposure by way of a fat biopsy, since some of its metabolites are also produced from other chlorinated hydrocarbons or are present as contaminants in the environment. Based on one worker occupationally exposed to hexachloroethane, Selden et al. (1993) estimated that the plasma half-life in humans was several days, but less than one week. A clearance half-life in rats of 2.5 days was reported for hexachloroethane absorbed from the diet (Gorzinski et al. 1985). Therefore, similar to measurement of hexachloroethane in blood, urine, and feces, hexachloroethane in body fat is representative of current exposures rather than exposures that occurred weeks or months before testing. 

The relative ratio of regioisomers of PCDD/F and other chlorinated compounds formed in incinerators is called the incineration pattern. The pattern can be derived from statistical analysis of a large number of measurements of the same plants, and can be used for elucidation of thermal formation mechanisms in plants. In principle regioisomers can be formed either by stereospecific chlorination or dechlorination processes. The pattern has also been used as a part for explaining of the formation mechanism of PCDD/F and other chlorinated compounds formed in incinerations (see Figure 8.4). 

Gas-diffusion flow injection analysis is capable of detecting very low concentrations of chlorine dioxide in water (i.e., detection limit is 5 ppb). A chemiluminescence flow-through detector cell is used to measure the concentration chlorine dioxide as a function of chemiluminescence intensity. A gas diffusion membrane separates the donor stream from the detecting stream and removes ionic interferences from iron and manganese compounds, as well as from other oxychlorinated compounds, such as chlorate and chlorite (Hollowell et al. 1986 Saksa and Smart 1985). 

The solvent extract should be subjected to one or more cleanup steps for the removal of interfering substances. The presence of phthalate esters, sulfur, or other chlorinated compounds can mask pesticide peaks. The extract should, therefore, be cleaned up from the interfering substances using a florisil column or by gel permeation chromatography (see Chapter 1.5). The distribution patterns for the pesticides in the florisil column fractions are presented in Table 2.20.2. 

Newsome, W.H., Ryan, J.J., 1999. Toxaphene and other chlorinated compounds in human milk from northern and southern Canada A comparison. Chemosphere 39, 519-526. 

They may be differentiated from other chlorinated hydrocarbon compounds (e.g., solvents) by molecular weight. Organochlorine insecticides, by virtue of their cyclic structure, have molecular weights ranging from 291 to 545, whereas chlorinated hydrocarbon solvents and fumigants have molecular weights that generally are less than 236. 

However, together with other chlorinated compounds like PCBs and CFCs, it possesses noxious effects on environment, particularly a high ozone potential depletion. It was, in fact, classified in the IV group among CFCs and so its use was banned, in developed countries, from 1996. 

Background Toxaphene is a complex mixture (>670 compounds) of chlorinated bornanes and bomenes that was used as an insecticide for 40 years from 1945. Many other chlorinated compounds entering the environment over the same period... 

Phosgene can be prepared from carbon monoxide, from halogenated hydrocarbons, from carbonaceous materials, from carbon dioxide, carbonyl sulfide or carbon disulfide, and from other oxygenated compounds [39]. The method based on the chlorination of carbon monoxide is by far the most important and has been scaled-up for the commercial manufacture of phosgene. 

The purity of oxygen from chlorate candles before and after gas filtration is indicated in Table 2. A particulate filter is always used. Filter chemicals are HopcaUte, which oxidizes CO to CO2 molecular sieves (qv), which remove chlorine compounds and basic materials, eg, soda lime, which removes CO2 and chlorine compounds. Other than H2O and N2, impurity levels of <1 ppm can be attained. Moisture can be reduced by using a desiccant (see Desiccants). Gas purity is a function of candle packaging as well as composition. A hotter burning unit, eg, one in which steel wool is the binder, generates more impurities. 

By-products from EDC pyrolysis typically include acetjiene, ethylene, methyl chloride, ethyl chloride, 1,3-butadiene, vinylacetylene, benzene, chloroprene, vinyUdene chloride, 1,1-dichloroethane, chloroform, carbon tetrachloride, 1,1,1-trichloroethane [71-55-6] and other chlorinated hydrocarbons (78). Most of these impurities remain with the unconverted EDC, and are subsequendy removed in EDC purification as light and heavy ends. The lightest compounds, ethylene and acetylene, are taken off with the HCl and end up in the oxychlorination reactor feed. The acetylene can be selectively hydrogenated to ethylene. The compounds that have boiling points near that of vinyl chloride, ie, methyl chloride and 1,3-butadiene, will codistiU with the vinyl chloride product. Chlorine or carbon tetrachloride addition to the pyrolysis reactor feed has been used to suppress methyl chloride formation, whereas 1,3-butadiene, which interferes with PVC polymerization, can be removed by treatment with chlorine or HCl, or by selective hydrogenation. 

Yields of propylene chlorohydrin range from 87—90% with dichloropropane yields of 6—9%. The dichloropropane is not only a yield loss but also represents a disposal problem as few uses are known for this material. Since almost all the propylene chlorohydrin is dehydrochlorinated to propylene oxide with lime or sodium hydroxide, none of the chlorine appears in the final product. Instead, it ends up as dilute calcium or sodium chloride solutions, which usually contain small amounts of propylene glycol and other organic compounds that can present significant disposal problems. 

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