ng of the water, and
not till then. In that process the soap is entirely wasted, and the
fatty acids in it form, with the lime and magnesia, insoluble compounds
called lime and magnesia soaps, which are sticky, greasy, adhesive
bodies, that precipitate and fix some colouring matters like a mordant.
We have in such cases, then, a kind of double mischief--(i) waste of
soap, (ii) injury to colours and dyes on the fabrics. But this is not
all, for colours are precipitated as lakes, and mordants also are
precipitated, and thus wasted, in much the same sense as the soaps are.
Now by taking a soap solution, formed by dissolving a known weight of
soap in a known volume of water, and adding this gradually to hard water
until a permanent lather is just produced, we can directly determine the
consumption of soap by such a water, and ascertain the hardness. Such a
method is called Clark's process of determination or testing, or Clark's
soap test. We hear a great deal just now of soaps that will wash well in
hard water, and do wonders under any conditions; but mark this fact,
none of them will begin to perform effective duty until such hard water
has been rendered soft at the expense of the soap. Soaps made of some
oils, such as cocoa-nut oil, for example, are more soluble in water than
when made of tallow, etc., and so they more quickly soften a hard water
and yield lather, but they are wasted, as far as consumption is
concerned, to just the same extent as any other soaps. They do not,
however, waste so much time and trouble in effecting the end in view,
and, as you know, "Time is money" in these days of work and competition.
After making a soap test as described above, and knowing the quantity of
water used, it is, of course, easy to calculate the annual loss of soap
caused by the hardness of the water. The monthly consumption of soap in
London is 1,000,000 kilograms (about 1000 tons), and it is estimated
that the hardness of the Thames water means the use of 230,000 kilograms
(nearly 230 tons) more soap per month than would be necessary if soft
water were used. Of course the soap manufacturers around London would
not state that fact on their advertising placards, but rather dwell on
the victorious onslaught their particular brand will make on the dirt in
articles to be washed, in the teeth of circumstances that would be
hopeless for any other brand of soap! I have referred to the sticky and
adhesive character of the compounds calle