20. The Variety of Organic         Compounds   Previous PageNext Page

Hydrolysis of natural fats with a base (usually NaOH or KOH) is called saponification - literally, "soap making":

One difficulty with natural soaps is that their calcium and magnesium salts are insoluble. If soap is added to hard water containing and , a greasy soap scum of calcium and magnesium stearate results. One solution to the problem is to use so much soap that all of the divalent cations are precipitated as scum, and more soap is left for cleaning purposes. This is messy and wasteful. Another solution is to remove the divalent cations ahead of time, and to replace them by via and ion-exchange resin in a water-softener. A third possibility is to use artificial detergents whose calcium and magnesium salts are soluble.


Sodium lauryl sulphate is one such detergent:

The trouble with many of these compounds is that they are not biodegradable, and eventually will pollute water supplies. The carboxylic acids are "natural" in the sense that they can be used as food by a host of bacteria, and are broken down eventually to and , to blend into the environment. Never having been faced with hydrocarbon sulfates prior tot he coming of man, bacteria have not evolved the machinery to use such compounds. They remain untouched in water and soil, occasionally leading to such monstrosities as rivers covered with detergent foam. Biodegradable detergents have been developed recently, which are not precipitated by calcium and magnesium ions, yet which can be eaten by bacteria.

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