| Water is either hard or soft. As it falls from the clouds, it is pure
and soft until it comes in contact with gases and solids, which are dissolved
by it and change its character. It is definitely known that the last of
the water that falls in a shower is much better than the first, as the
first cleanses not only the air, but the roofs and other things with which
it comes in contact. In passing through certain kinds of soil or over rocks,
water dissolves some of the minerals that are contained there and is thus
changed from soft to hard water.
If sewage drains into a well or water supply, the water is liable to
contain bacteria, which will render it unfit and unsafe for drinking until
it is sterilized by boiling. Besides rain water and distilled water, there
is none that is entirely soft; all other waters hold certain salts in solution
to a greater or less degree.
The quality of hardness, which is present in nearly all water, is either
temporary or permanent. Water is temporarily hard when it contains soluble
lime, which is precipitated, that is, separated from it, upon boiling.
Every housewife who uses a teakettle is familiar with this condition. The
lime precipitated day after day clings to the sides of the vessel in which
the water is boiled, and in time they become very thickly coated.
Permanent hardness is caused by other compounds of lime that are not
precipitated by boiling the water. The only way in which to soften such
water is to add to it an alkali, such as borax, washing soda, or bicarbonate
of soda. |
