It is in this direction, therefore, that we must look for the
production of a safe and reliable antiseptic soap.
There is not much exact knowledge as to the usefulness of such
additions to soap as borax and glycerin. They are frequently added,
and highly spoken of in advertisements. Borax is a mild alkaline body,
and as a detergent is probably equivalent to a slight excess of
caustic soda. Glycerin, although originally considered an emollient,
probably on account of its source and physical properties, is in
reality, to some skins at least, a slight irritant. It is, in fact, an
alcohol, not a fat. It does not pre-exist in fats, but is formed when
the fat is decomposed by alkali or steam.
In ordinary cases, soap owes its detergent effect to a decomposition
which occurs when it is put in water.
A perfectly neutral soap, that is, one which contains the exact
proportion of alkali and fat acid, will, when placed in cold water,
decompose into two portions, one containing an excess of the acid, the
other an excess of alkali. The latter dissolves, and gives a slightly
alkaline solution; the former precipitates, and gives the peculiar
turbidity constituting "suds." These reactions must be kept in mind in
determining the effect of the addition of any special substance to the
soap.--_The Polyclinic.
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