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54
WATER-SUPPLY.
consumes from 13 to 19 times as much soap as
distilled water would consume*.
The chemical constitution of these waters occasions
another inconvenience. Their carbonate of
lime is held in solution (in the chemical form of
bicarbonate) by an excess of carbonic acid: under
the influence of heat this excess is gradually disengaged
and driven off; consequently, as they approach
the boiling point, they begin to precipitate
the earthy salt which that gas was instrumental in
dissolving. Each gallon of water under these circumstances
would deposit from ten to fifteen grains
of earthy matter on the interior of whatever vessel
might contain it, or on the surface of whatever
solid—linen or mutton, might be contained in the
boiler. Hence arises the well-known furring of vessels
in which such waters have habitually been
boiled.
*It has been alleged that, by the use of soft water, the saving
in soap would probably be equivalent to the whole of the money
at present expended on water-supply; and that in the article of
tea, the economy would amount to about one third of the tea now
consumed in the metropolis. It strikes me as possible that, in
forming these estimates, the argument may have proceeded too
much from a consideration of the hardness of London waters in
their unboiled state; and that sufficient allowance may not have
been made for the change which boiling produces. If boiling
were prolonged for some hours before culinary or detergent use of
the water, the results (for tea or soap) would be identical with
those produced under the employment of soft water. Notoriously
this precaution is not taken: but to avoid disputable ground, I
confine myself to the fact of considerable pecuniary loss, arising
from the cause in question, and I avoid any attempt to determine
its exact amount.