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1933]
50
use water softening apparatus. Within recent years smaller "Water Softeners"
have been made for domestic use. Questions have been addressed to our department
as to the use of these, the change effected on the water, and any possible
effect on the health of the person drinking such softened water. A brief nontechnical
outline of the principle on which the domestic water softener works and
the chemical analysis of such a treated water is therefore of interest. A number of
substances or preparations known as "permutits" are used. These, when added
to hard water, cause certain chemical changes to occur. They take out of the
water the hardness-causing substances, the calcium and magnesium salts and in
their turn exchange for these, the soda which the "permutit" preparation contains.
This soda readily dissolves in the water and has no effect further than causing the
softened water to become slightly alkaline. (This soda will act on aluminium
if used as kettles, etc. and blacken the water.) The basic constituents of the
"permutit" preparation and the water-hardness substance are exchanged, hence
the name "base exchange" given to the method. "Permutit" preparations are
artificially produced silicates obtained by melting china clay (Kaolin) with quartz
and sodium carbonate, and washing with water. The result is a double silicate
of soda and aluminium called Synthetic Sodium—aluminium—silicate, this base
exchange material is known by various trade names, such as Permutit, Basex,
Doucil, etc. After a base exchange water softener has been in use it gradually
loses efficiency and has to be restored or revivified. This is quite a simple matter.
A strong solution of common salt in water when passed through the material
restores its water softening properties; it is necessary after using the salt to
thoroughly wash the material with ordinary water, before use.

The above data show that the calcium and magnesium salts have been entirely
removed by the softening process adopted. The resulting water contains all the
mineral salts in the form of sodium and potassium, thus the calcium bicarbonate
naturally present in London water is converted into sodium bicarbonate, hence
the water is slightly alkaline.
For cooking vegetables, boiling kettles (not aluminium), washing purposes,
and for toilet and domestic purposes, the advantages of soft water are well
known and appreciated.
A better infusion of tea, for instance, is obtained from soft water than from
hard water, hence less tea need be used where soft water is available.
No deleterious ingredient could be detected in the sample of softened water
submitted for examination.
A water softened by this process would not be suitable for young children
as it is devoid of calcium, an element essential for bone growth.