TM 5-6630-215-12
(b)
The Free Chlorine Residual Test is conducted as folows:
(1) Select two (2) Clean Comparator Sample Cells.
(2) Fill one cell to the 15 ml mark with test water.
(3) Insert the cell into the right hand cell compartment
of the comparator.
NOTE
This cell, when filled to the mark, compensates
for color and turpidity.
The omission of this
step may cause serious errors.
(4) Collect just enough test water to cover the bottom of
the 2nd sample cell.
(5) Add two DPD Tablets No.
1 to the 2nd sample cell and
crush it with the stirring rod.
Fill the sample cell to the 15 ml
mark with test water and insert it into the left hand cell compartment
of the comparator.
Compare the sample with the color standard of the
appropriate disc as rapidly as possible.
Record the result which is
the closest match at the value of the Free Residual Chlorine level of
the test sample.
Interpolation between the two values may be
necessary.
(6) When the test has been completed, remove both sample
cells from the comparator, empty the samples and wash the cells with
clean water.
f.
Conductivity Meter - Total Dissolved Solids (fig. 2-17 and
table 2-9).
(1) The Total Dissolved Solids (Conductivity) Meter is a compact
meter operating on an electrical conductivity principle and reads
directly in parts per million from 1 to 5000 on three ranges 0-50,
0-500 and 0-5000 (to 50,000 or more with the RE 10 range extension
accessory).
See figure 2-17 and table 2-9 for location and function
of controls and indicators.
It is self-contained, calibrated against
a standard sodium chloride solution, and has a permanent built-in cell
with fully automatic
temperature compensation from 10°
- 71°C
(50° - 160°F) and is powered for 1000 or more tests by a 9 volt
transistor battery.
(a) The built-in electrode conditioning feature automatically
operates each time the button is pushed with a sample in the cell,
thus insuring consistent results every time.
A small initial downward
swing of the meter pointer with some samples is a result of this
conditioning action.
This action is powerful and removes normal films
of oil and dirt but if dirty samples, particularly scaling types, are
allowed to repeatedly dry in the cell,
a film will build up that
reduces accuracy.
Wherever visible films of oil, dirt or scale
2-68
