Chlorine controversy

This was the opening of the so called chlorine controversy between Dr. John Davy and Dr. Murray, fervent supporter of the official theory. This debate took the form... 

R. Stone, Science, 1994, 265, 308 estrogen mimics and the chlorine controversy. 

The presumed nonintercalation of a given compound may, however, be due to the fact that appropriate experimental conditions for intercalation have not yet been found. Thus, some of the rare-earth chlorides originally considered not to intercalate Cll, V5), do, in fact, do so in the presence of a complexing agent S21). In addition, the role of chlorine in compound formation has been the subject of controversy. Whereas Croft (Cl) considered the presence of an excess of chlorine to be nonessential, it has since been shown to be a sine qua non for compound formation (D3, RIO, H13, Rll, S22, B17, H25). Moreover, contrary to earlier assumptions (RIO), chlorine does not act as a catalyst, but is incorporated into the graphite to a greater or lesser extent Rll, D3). In cases where the presence of chlorine is apparently not required... 

The detection of a potent dioxin impurity in a major herbicide has focused attention on the nature of chlorinated impurities in pesticides, and in a larger sense, impurities in all chlorinated industrial compounds used extensively in man s environment. The present 2,4,5-T controversy is overshadowed by the dioxin problem. Major disagreement still exists on their relative contributions to the teratogenic effects observed in chicks and the validity of interpretation of high dosage rates used to achieve these effects. We have avoided any assessment of the health-related aspects of dioxins but have dealt almost exclusively with dioxins as an environmental entity. 

C05-0071. Freons (CFCs) are compounds that contain carbon, chlorine, and fluorine in various proportions. They are used as foaming agents, propellants, and refrigeration fluids. Freons are controversial because of the damage they do to the ozone layer in the stratosphere. A 2.55-g sample of a particular Freon in a 1.50-L bulb at 25.0 °C has a pressure of 262 torr. What is the molar mass and formula of the compound ... 

As Table 21-1 suggests, molecular chlorine is a tremendously versatile industrial chemical. This element is a leading industrial chemical because of this versatility rather than any single application, although polymers account for about one third of its uses. In recent years, however, the industrial use of chlorine has come under strong attack from many environmentally conscious groups. One major reason is that dioxins, one class of by-products of chlorine reactions, have a very detrimental effect on biosystems. The controversy over industrial chlorine is described in our Chemistry and the Environment Box on page 936. 

The hydrogen-chlorine chain reaction has proved to be one of the most controversial systems yet studied. After thirty years of investigation Bodenstein43 was able to say in 1931 that every worker on the photochemical synthesis of HC1 had produced his own mechanism even as late as 1940 little positive information had been obtained. However, the accumulated techniques and experience had firmly established the importance of atom chain reactions. The mechanism of photo-initiation and propagation is the same as for the hydrogen bromide photosynthesis, a non-branching chain reaction... 

Some people object to the chlorination of water, and prefer to drink bottled spring water. There is controversy over the level of risk associated with chlorination, and over the possible benefits of spring water. For example, hypochlorous acid reacts with traces of organic materials in the water supply. These reactions can produce toxic substances, such as chloroform. Supporters of chlorination believe that these substances are present at very low, safe levels, but opponents of chlorination disagree. Complete the following practice problems to help you decide on your own opinion of chlorination. 

Through the natural processes of the UV rays of the sun passing through this layer, the absorbs the rays and is broken down to molecules and O atoms. This process is reversible, and ozone (O ) is constantly being reformed from UV effects on However, the separation can be accelerated faster than the reformation of new by induction of other chemical gases into the ozone layer. Of particular concern is that chlorine from CFCs and from other sources, such as the ocean and volcanic eruptions, combines with atomic oxygen that is broken down from Oj by UV radiation. It then forms chlorine monoxide (CIO), which means the atomic oxygen is not available for reformation into O by UV radiation. Herein lie the potential problem and the controversy. 

Although there has been some controversy over whether there is indeed a true ozone deficit problem (e.g., Crutzen et al., 1995), a combination of measured concentrations of OH, HOz, and CIO with photochemical modeling seems to indicate that it may, indeed, exist (Osterman et al., 1997 Crtuzen, 1997), although the source of the discrepancy remains unclear. Measurements of CIO in the upper stratosphere have found concentrations that are much smaller (by a factor of 2) than predicted by the models (e.g., Dessler et al., 1996 Michelsen et al., 1996). Because of the chlorine chemistry discussed later, model overestimates of CIO will also result in larger predicted losses of 03 and hence smaller concentrations. 

The impact on the generation of active forms of chlorine by heterogeneous reactions on the A1203 particles is somewhat controversial (Prather et al., 1990 Danilin, 1993 Denison et al., 1994 Jackman et al., 1996). For example, the reaction of C10N02 with HC1 to generate Cl2, for example, proceeds relatively rapidly (reaction probability of 0.02) at 208-223 K on hy-droxylated a-alumina (Molina et al., 1997). However, it appears that this is not unique to the A1203 surface but rather is due to water layers adsorbed on the solid. 

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