Chlorine natural sources

Bromine is substantially less abundant in crustal rocks than either fluorine or chlorine at 2.5 ppm it is forty-sixth in order of abundance being similar to Hf 2.8, Cs 2.6, U 2.3, Eu 2.1 and Sn 2.1 ppm. Like chlorine, the largest natural source of bromine is the oceans, which contain 6.5 x 10 %, i.e. 65 ppm or 65mg/l. The mass ratio Cl Br is 300 1 in the oceans, corresponding to an atomic ratio... 

The chlorophylls produced by bacteria, algae and plants are a natural source of chlorins. The isolation of chlorophylls from natural material is known to be difficult because of their extreme sensitivity to various reactions, such as enolization, epimerization, allomerization, de-methoxycarbonylation, solvolysis, demctalation, dephytylation, photooxidation, etc. Often the... 

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. 

There are many natural sources of chlorine compounds, which is not surprising considering that it is the 20th most abundant element. Salt and salt water are widely available the Great Salt Lake contains 23% salt, and the Dead Sea contains about 30%. Because salt is so abundant, most minerals that contain chlorine are not important sources for economic reasons. Bromine is found in some salt brines and in the sea, as are some iodine compounds. 

There are no known natural sources of hexachlorobutadiene which contribute to environmental levels. The main source of hexachlorobutadiene in the United States is its production as a by-product of chlorinated hydrocarbon synthesis. An estimated 100,000 pounds of this by-product are released to the environment each year. The majority of hexachlorobutadiene-containing waste is disposed of by incineration, with lesser amounts disposed by deep well injection and landfill. 

In his first research on bromine, published in the Annales de Chimie et de Physique in 1826, Balard prepared and characterized many of its compounds and described some of its most important natural sources. This astonishingly rapid progress was possible only because of the close resemblance of bromine to chlorine and iodine, which were already well known. 

An important piece of evidence that some of this chlorine comes from the breakdown or CFCs was the unusually high levels of fluorine compounds detected in the Antarctic stratosphere. Whereas chlorine compounds come from a number of natural sources, fluorine compounds in nature are relatively rare. The source of this stratospheric fluorine, therefore, is most likely chlorofluoro-carbons. In addition to elevated fluorine levels, evidence of ozone depletion... 

For practical purposes, a majority of elements have a constant mixture of natural isotopes. For example, mass spectrometric studies of chlorine show that the element consists of 75.53% n35Cl atoms (mass = 34.97 u) and 24.47% n37Cl atoms (mass = 36.95 u). Experience has shown that any sample of chlorine from a natural source will consist of these two isotopes in this proportion. 

Stratospheric source gases - A variety of gases transport chlorine into the stratosphere. These gases are emitted from natural sources and human activities. For chlorine, human activities account for most that reaches the stratosphere. The CFCs are the most abundant of the chlorine-containing gases released in human activities. Methyl chloride is the most important natural source of chlorine ... 

Iodine is produced by similar methods, namely, oxidation of the iodide anion from brines by chlorine. However, iodine is also produced in a reductive process by reacting NalOs, extracted from the natural source of Chilean saltpeter, with sodium hydrogen snffite. The pentavalent iodine is reduced to iodide (equations), which is then treated and oxidized with a sufficient amonnt of the mother liquor to liberate elemental iodine (equation 5). In contrast to chlorine and bromine, which have large industrial uses, iodine has no predominant commercial use. 

Figure 6 traces the major exchange reactions in the SOURCE — RADICAL RESERVOIR system. The dominant natural source of chlorine in the stratosphere is CH3CI the main synthetic contribution is from CCI4, CF2CI2 and CFCI3. Atomic chlorine and chlorine monoxide are... 

Palmer T. Y. (1976) Combustion sources of atmospheric chlorine. Nature 263, 44-46. 

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