Chlorinated hydrocarbons early

In early designs, the reaction heat typically was removed by cooling water. Crude dichloroethane was withdrawn from the reactor as a liquid, acid-washed to remove ferric chloride, then neutralized with dilute caustic, and purified by distillation. The material used for separation of the ferric chloride can be recycled up to a point, but a purge must be done. This creates waste streams contaminated with chlorinated hydrocarbons which must be treated prior to disposal. 

The performance of SCWO for waste treatment has been demonstrated (15,16). In these studies, a broad number of refractory materials such as chlorinated solvents, polychlorinated biphenyls (PCBs), and pesticides were studied as a function of process parameters (17). The success of these early studies led to pilot studies which showed that chlorinated hydrocarbons, including 1,1,1-trichloroethane /7/-T5-6y,(9-chlorotoluene [95-49-8] and hexachlorocyclohexane, could be destroyed to greater than 99.99997, 99.998, and 99.9993%, respectively. In addition, no traces of organic material could be detected in the gaseous phase, which consisted of carbon dioxide and unreacted oxygen. The pilot unit had a capacity of 3 L/min of Hquid effluent and was operated for a maximum of 24 h. 

Bishop CA, Lean DR, Brooks RJ, Carey JH, Ng P. 1995b. Chlorinated hydrocarbons in early life stages of the common snapping turtle (Chelydra serpentina serpentina) from a coastal wetland on Lake Ontario, Canada. Environ Toxicol Chem 14 421 26. 

Muller had several clues to guide his search. First, he knew from Henri Martin s mothproofing work that a chlorinated hydrocarbon worked as a gastric moth poison. Second, his early experiments showed him that compounds with the group CH2C1 had some insecticidal effect. Third, a 1934 article in the Journal of the Chemical Society of London described the preparation of diphenyltrichloroethane, which Muller found to be somewhat poi-... 

A variety of compounds have been evaluated for developmental immunotoxicity. Early work with chlorinated hydrocarbon insecticides revealed that lactating women exposed to the insecticide chlordane, had residues of chlordane in their breast milk.97 A study was performed in mice to determine if chlordane might alter the immune system of mouse pups exposed to chlordane via the dam s milk.98 Female pups displayed... 

Some recent developments and future trends in international regulation of chemical contaminants in food are discussed in section 12.5. It is attempted to foresee some issues that could be of interest and concern for food scientists and legislators dealing with contaminants in food in the early part of the new millennium. Certainly, persistent organic pollutants, many of which are chlorinated hydrocarbons, and some of which have been used in the past and in fact may still be used in parts of the world as pesticides, will be among those issues of justified concern. 

Chlorinated hydrocarbons and chlorine (early 1950s) Large number of units... 

In the 1940s, many chlorinated hydrocarbon insecticides were developed though they did not come into widespread use until the 1950s. Common examples include aldrin, dieldrin, heptochlor, and endrin. However, in spite of their early promise, these organochlorine insecticides are now much less used because of their environmental pollution impact. 

Early studies of the radiation chemistry of chlorinated hydrocarbons demonstrated the formation of molecular cations of aromatic hydrocarbons with half-lives of the order of a few micoseconds [26]. In solutions containing two different aromatic solutes, it was possible to measure the rate of electron transfer from the neutral molecule to the radical cation. Some specific examples of other studies are given below. 

The kinetics of chlorinated hydrocarbon reactions exhibit several distinguishing features when compared to the reactions of analogous hydrocarbons. " First, as a consequence of the weaker C-Cl bond dissociation energies, CHCs decompose at temperatures that are significantly lower than the analogous hydrocarbons. This leads to the early production of Cl radicals, thereby establishing the requisite free radical chain reactions, which destroy the parent CHC and lead to gas phase polymerization, ultimately forming soot. 

Volatilization and vapor phase transport are important processes in the dissipation of even the so-called nonvolatile pesticides, such as the chlorinated hydrocarbons. The vapor pressure or the vapor saturation density is therefore an important parameter to assess the persistence of the pesticide. Much work was done very early in the era of the (persistent) pesticides. Table 8.3 shows the vapor pressure and water solubility of some important chlorinated pesticides and contaminants in pesticide formulations. 

Because rootworm insecticides are most commonly applied at planting, 4-8 weeks prior to rootworm egg hatch, it was early recognized that the inherently rapid degradation rate of some of these insecticides precluded their effective use (5). However, most provided effective control without the undesirable environmental impact of the chlorinated hydrocarbons. By 1973 roughly 20-30 million acres of midwest corn were treated annually with soil insecticides (6), and corn had become the leading crop for use of soil Insecticides. 

The poisonous effect of arsenic has been known since ancient times and its application against insects was recommended as early as the seventeenth century in a book by John Worlidge (Munro, 1946). The use of various inorganic preparations for plant protection increased to several hundred million tons per year by the 1940s, but since then they have been replaced to a considerable extent by chlorinated hydrocarbon insecticides. 

The best known of these is the ozonation of tertiary amines to amine oxides (II) (i). Henbest and Stratford (11) and Shulman (17) have shown that competing with this is an ozone attack on the alpha position of an alkyl side chain to produce various decomposition products of III. Henbest (11) showed that amine oxide formation is favored in chloroform and methanol, while side chain oxidation is predominant in hydrocarbon solvents. Also of considerable interest are the reported conversions, during ozonation, of phenylenediamines to Wursters salts (VII) (8, 14), of liquid ammonia to ammonium ozonate (VA) at a low temperature 18), and of amines to amine hydrochlorides (VB) in chlorinated hydrocarbon solvents 17, 19), Finally, an early report states that azobenzene and quinone are obtained upon ozonation of aniline (15). 

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