Dissolved halogenated organic substances

Seawater contains considerable amounts of dissolved halogenated organic substances. The following chapter deals with the low relative molecular mass fraction, i.e., substances with one to four carbon atoms. This group of compounds is often called halocarbons or volatile halogenated organic compounds (VHOC). 

Tin does not react directly with nitrogen, hydrogen, carbon dioxide, or gaseous ammonia. Sulfur dioxide, when moist, attacks tin. Chlorine, bromine, and iodine readily react with tin with fluorine, the action is slow at room temperature. The halogen acids attack tin, particularly when hot and concentrated. Hot sulfuric acid dissolves tin, especially in the presence of oxidizers. Although cold nitric acid attacks tin only slowly, hot concentrated nitric acid converts it to an insoluble hydrated stannic oxide. Sulfurous, chlorosulfuric, and pyrosulfiiric acids react rapidly with tin. Phosphoric acid dissolves tin less readily than the other mineral acids. Organic acids such as lactic, citric, tartaric, and oxaUc attack tin slowly in the presence of air or oxidizing substances. 

Like supercritical carbon dioxide, supercritical water is a very interesting substance that has strikingly different properties from those of liquid water. For example, recent experiments have shown that supercritical (superfluid) water can behave simultaneously as both a polar and a nonpolar solvent. While the reasons for this unusual behavior remain unclear, the practical value of this behavior is very clear It makes superfluid water a very useful reaction medium for a wide variety of substances. One extremely important application of this idea involves the environmentally sound destruction of industrial wastes. Most hazardous organic (nonpolar) substances can be dissolved in supercritical water and oxidized by dissolved 02 in a matter of minutes. The products of these reactions are water, carbon dioxide, and possibly simple acids (which result when halogen-containing compounds are reacted). Therefore, the aqueous mixture that results from the reaction often can be disposed of with little further treatment. In contrast to the incinerators used to destroy organic waste products, a supercritical water reactor is a closed system (has no emissions). 

A mixture which is to be examined is broken down into its constituents as far as possible by treating it with various substances, which either dissolve certain constituents of the mixture as such or convert them into soluble compounds. In effecting such solutions the following substances are frequently used Water, which removes from the mixture substances soluble in water a solution of hydrochloric acid, which removes basic substances insoluble in water a solution of sodium hydroxide, which dissolves acids insoluble in water concentrated sulphuric acid, which separates many oxygen compounds from hydrocarbons and certain halogen derivatives and organic solvents which, in certain cases, may dissolve certain constituents of the mixture and not others. 

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