(1) A chlorination kit (figure 6-3) is available to all units for use in
chlorinating water and testing it for the proper chlorine residual. The kit contains
calcium hypochlorite ampules (0.5 gram) for disinfecting water, together with three
plastic tubes and three vials of orthotolidine tablets for use in determining the chlorine
residual. The vials of orthotolidine tablets are packed inside the plastic tubes. Each of
the plastic tubes has a band of a different shade of yellow around it. The lightest shade
of yellow indicates 1 ppm; the medium shade, five ppm; and the darkest shade, ten ppm.
These figures are printed on the tubes. An orthotolidine tablet is placed in the plastic
tube appropriate for the residual desired, the tablet is dissolved with water from the
batch being treated with chlorine, and the resulting yellow color is compared with that of
the yellow band near the top of the comparator tube. A color equal to that color on the
comparator tube indicates a total chlorine residual equal to that marked on the tube.
Figure 6-3. Items in chlorination kit.
Total chlorine residual may or may not be the same as free available chlorine
(FAC). If, however, total available chlorine residuals are obtained in the
range of 5 to 10 ppm at point of treatment, it is highly likely that a significant
portion of the residual will be primarily FAC.