TM 5-6630-215-12
a.
Carefully read the instructions given in the test procedure.
Fill the titration vial with the proper amount of water sample.
The
necessary indicator, buffer, etc.,
should be added as outlined in the
instruction and mixed with the test sample.
b.
Remove the cap from the titration reagent bottle, thus exposing
the special plastic fitting.
The plunger of the burrette is depressed
so that the plunger tip is resting on the bottom of the barrel. This
expels the air from the barrel with the exception of a small amount of
air in the constricted tip.
The tip of the micro burette is pressed
downward into the hole in the fitting.
c. With the burette firmly inserted in the fitting, invert the
bottle so that the solution in the bottle covers the tip of the
burette.
(This is the same action used by the doctors and nurses when
they fill hypodermic syringes.)
Withdraw the plunger which will fill
the barrel with titration solution.
The plunger is withdrawn until
the bottom of the plunger tip is opposite the zero mark on the grad-
uated scale.
Turn the bottle right side up before removing the
burrette.
Wipe the tip of the micro burette of any solution adhering
to the outside of the tip.
Recap the bottle of titrating solution.
On some occasions, a small air bubble may appear under the tip of the
plunger.
Usually the air bubble can be expelled by partially filling
the barrel with titrating solution, then expelling the solution back
into the inverted regent container.
As the lowest graduation of the
scale (line 20) is above the bottom of the barrel, the presence of
this air bubble will not affect the accuracy of the reading. Be
certain that the plunger tip is level with the zero graduation and
that the final reading is made at the point on the scale opposite the
bottom of the plunger.
d.
Hold the titration vial in one hand and the micro burette in
the other.
Slowly depress the plunger of the micro burette to expel
the titration reagent.
A slight rotating or twisting motion permits
the plunger to move smoothly as it is depressed.
e.
Swirl the titration vial (fig. 2-1) so that each addition of
titration reagent is thoroughly mixed with the sample.
Continue
adding titration reagent until the color change takes place in the
test sample.
If no color change is noted by the time the plunger tip
reaches line 20, refill the burette from the titration reagent bottle,
wipe off the tip, and continue adding titration reagent until the
color change is observed.
f.
Do not count the number of drops of titration reagent added to
the sample.
The amount of titration reagent added is recorded in
micro burette divisions.
With experience, drops of differnet sizes
may be expelled from the micro burette depending upon the angle at
which it is held.
If the micro burette is held vertically, the drops
are large.
As the burette is held more in a horizontal position, the
drop size becomes smaller (this is useful when approaching the color
endpoint and smaller increments of titration reagent are desired).
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