TM 5-4610-218-12
2-20.
(7) Indicator Tube Reading. When taking
color readings with the indicator tube, the readings
(2) Remove two knurled screws on front of
must be made within one minute of adding the
comparator and lift off front cover. Install chlorine
chemicals to the tube.
disc on comparator body so that the recess at the
center of the disc fits over a hub on the body, replace
2-19. Total Chlorine Residual.
front cover and install knurled screws.
a. General. The measurement of chlorine in
water is extremely important since the bacterial pu-
gaging two pins in the prism in matching holes in
rity of the water is governed by the amount of chlo-
the front cover.
rine present. Standard practice calls for the addi-
(4) Wash two sample tubes in the water to be
tion of sufficient chlorine (calcium hypochlorite) to
tested and fill both tubes to the graduation mark
produce a slight excess of chlorine after the chlorine
with the water to be tested. The samples should not
and water have been in contact for 30 minutes. This
be collected until the water and calcium hypo-
excess, or residual chlorine, is measured by the com-
chlorite have been in contact for 30 minutes. This
parator and is used to determine the correct chlo-
will allow proper time for mixing. Place the first
rine dosage. Sufficient calcium hypochlorite should
tube in the right-hand compartment of the com-
be added in the settling tank to obtain the required
parator.
residual chlorine in the finished water. Residual
chlorine of finished water should be periodically
the graduation mark with orthotolidine indicator
checked and be in compliance with whatever value
solution and add solution to the second sample tube.
the Area Command Surgeon prescribes for water in
If the water is cold, hold the test tube in palm of
the particular area.
hand to bring the water temperature above 50F
b. Test Procedure.
(10C).
(1) See general test precautions in paragraph
Figure 2-25. Use of chlorine comparator.
occur within five minutes after the reagent has
(6) Place the second tube in the center com-
been added.
partment of the comparator. Make sure that both
sample tubes are pushed down as far as they will go
(7) Look through the eyepiece. Compare the
and wait until the sample in the center compart-
sample color with that of the standard by rotating
ment has developed its maximum color. This should
2-54
