Hach-Lange MTC10130 - Manual (Page 7)

The following directions represent a general procedure for doing a redox titration once the
sample is prepared for measurement.
1. Fill a 10 mL
burette with a
standard titrant
solution with a
normality that is
5-10 times that of
the sample. 2. Connect the
probe to the
meter. 3. Pipet a 50 mL
sample into a 150-
mL beaker. Stir
with a magnetic
stirrer throughout
the titration. 4. Add titrant in
0.5 to 1 mL
increments.
Record the
potential after
each addition.
Near the end
point, when large
potential changes
are seen, add
increments of
0.1 to 0.2 mL.
Continue the
titration 3 to 4 mL
past the end point. 5. Plot the
electrode potential
versus volume of
added titrant and
fit a smooth curve
through the points.
The end point is
the point of
inflection (the
point of greatest
slope).
6. Calculate the
normality of the
sample, N
x
, in
equivalents per
liter:
N
x
= (V
t
x N
t
) / V
x
where:
N
t
= normality of
titrant (Eq/L)
V
t
= volume of
titrant at end point
(mL)
V
x
= Volume of
sample (mL)
Run a check standard
The run check standard feature validates instrument performance between sample
measurements. Use the run check standard feature for periodic or user-defined interval
measurements of a traceable standard solution. Set the criteria for check standards from
the MTC101 Settings menu.
Note: Access control must be off or a valid password must be entered before any of the check
standard method options can be changed.
1. Push . The Full Access Options menu is shown.
2. Select Run Check Standard.
Note: Select the correct probe if two probes are connected to the meter.
7