5-14. DETERMINING CHLORINE RESIDUAL AND pH
The chlorine residual in water is measured with a comparator test kit (figure 5-6).
The comparator is a viewing device in which the color developed in a treated water
sample is compared with standard colors mounted on discs that can be inserted and
rotated in the comparator. The comparator has a dual use. Procedures and reagents
can be varied so that either the chlorine residual or the pH of a water sample can be
read directly from the colored disc matched by the water sample. The pH is important in
that the amount of free available chlorine required to kill the organisms in a given water
sample varies directly with the pH. For example, water with a pH of 10 requires five
times as much chlorine residual as water with a pH of seven. The water quality control
set, of which the color comparator is a component part, contains detailed instructions for
determining both the free available chlorine residual and the pH of a water sample.
Sets are found in engineer units, preventive medicine units, and Army medical
5-15. OTHER QUALITY TESTS
In addition to the determination of chlorine residual and pH, Corps of Engineers
personnel also conduct tests for turbidity, chlorine demand, salinity, alkalinity, chlorides,
Figure 5-6. Color comparator with case.