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CHLORINE
Because of its pronounced activity as a non-metal and its consequent tendency to combine with metals, chlorine is never found naturally in a free state. In the combined state, however , it is assumed to be one of the moderately abundant elements of the earth's crust. Chemists consider its most abundant natural com­pounds to be the chlorides of certain metals. Of these, sodium chloride is estimated to be the most abundant.
Experiments showed chlorine to be only slightly soluble in water. Its density is stated to be almost two and one-half times that of the air. Its litre under normal conditions weighs about 3,2140 grams.
We know chlorine to be a typical non-metal It resembles oxygen in some respects, but differs in showing more pronounced activity in its reactions with the metallic elements. Oxygen, on the other hand, is found to display a greater tendency to react with the non-metals.
Absolutely dry chlorine does not seem to attack metals; at least the reaction is very slow. Experiments prove chlorine to react with almost all of the non-metals. The reaction of hydrogen and chlorine is exothermic.
H2 + C12 -> HCl + 44000cal.
We should, therefore, expect these two elements to combine very readily and the product to be very stable. In the dark, however, hydrogen does not appear to combine with chlorine with appreciable velocity and the reaction seems to require the presence of a catalyst. In ordinary light the reaction is likely to take place slowly. In direct sunlight we see the reaction occur evidently.
Since chlorine combines very readily with free hydrogen, we should expect it also to react with compounds containing hydrogen. Natural gas, which is known to consist largely of methane(CH 4) continues to burn when a lighted jet of the gas is introduced into a cylinder filled with chlorine and hydrogen chloride and free carbon are produced.
With certain compounds, chlorine is stated to combine directly to form what are called addition compounds. Besides, chlorine may also be shown to react with compounds with certain chlorides in much the same manner as oxygen reacts with certain oxides. These reactions show chlorine to play its most characteristic role, that of a vigorous oxidizing agent.