F. Immediately squirt with force one dropper full of sodium arsenite into the
Figure 2-4. Modified OTA method, color comparator determination of free
available chlorine (continued).
G. Push both tubes down until tops are flush with top
of comparator. Hold the
comparator close to your eye and face a good light source. Rotate the color
disk until the color on the disc matches the color of the solution in the
indicator (left) tube.