action.

All of the apparatus for effecting such treatment of feed waters is
approximately the same in its chemical action, the numerous systems
differing in the methods of introduction and handling of the reagents.

The methods of testing water treated by an apparatus of this description
follow.

When properly treated, alkalinity, hardness and causticity should be in
the approximate relation of 6, 5 and 4. When too much lime is used in
the treatment, the causticity in the purified water, as indicated by the
acid test, will be nearly equal to the alkalinity. If too little lime is
used, the causticity will fall to approximately half the alkalinity. The
hardness should not be in excess of two points less than the alkalinity.
Where too great a quantity of soda is used, the hardness is lowered and
the alkalinity raised. If too little soda, the hardness is raised and
the alkalinity lowered.

Alkalinity and causticity are tested with a standard solution of
sulphuric acid. A standard soap solution is used for testing for
hardness and a silver nitrate solution may also be used for determining
whether an excess of lime has been used in the treatment.

Alkalinity: To 50 cubic centimeters of treated water, to which there has
been added sufficient methylorange to color it, add the acid solution,
drop by drop, until the mixture is on the point of turning red. As the
acid solution is first added, the red color, which shows quickly,
disappears on shaking the mixture, and this color disappears more slowly
as the critical point is approached. One-tenth cubic centimeter of the
standard acid solution corresponds to one degree of alkalinity.

[Illustration: 2640 Horse-power Installation of Babcock & Wilcox Boilers
at the Botany Worsted Mills, Passaic, N. J.]

Causticity: To 50 cubic centimeters of treated water, to which there has
been added one drop of phenolphthalein dissolved in alcohol to give the
water a pinkish color, add the acid solution, drop by drop, shaking
after each addition, until the color entirely disappears. One-tenth
cubic centimeter of acid solution corresponds to one degree of
causticity.

The alkalinity may be determined from the same sample tested for
causticity by the coloring with methylorange and adding the acid until
the sample is on the point of turning red. The total acid added in
determining both causticity and alkalinity in this case is the measure
of the alkalinity.

Hardness: 100 cubic centimeters