D3230_10 (13)
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The conductivity of
solutions is affected
by the temperature
of the specimen
when measurements are made.
The temperature of
the test specimen
at the time of measurement shall
be within 3 degrees Celsius
of the temperature at which the
calibration curves were made.
Establish a blank
measurement by following
the procedure in section
10.3 and 10.4 of the Written
Standard, omitting the
mixed salt solution.
When the indicated
electrode current is greater
than 0.25 milliamperes
at 120 volts AC,
water or another conductive
impurity is present,
and its source must be
found and eliminated
before calibration
can be completed.
Determine a blank
measurement for each time
fresh xylene or mixed
solvents is used.
Into a dry,
100-milliliter graduated
glass-stoppered mixing cylinder,
add 15 milliliters of xylene.
From a 10-milliliter
pipette, total delivery--
see section 6.3 of
the Written Standard--
or 10-milliliter
graduated cylinder--
see section 6.3.1 of the Written
Standard when applicable--
add 10 milliliters
of neutral oil.
Rinse the 10-milliliter
pipette or 10-milliliter
graduated cylinder with
xylene until free of oil.
Make up to 50
milliliters with xylene.
Stopper and shake the cylinder
vigorously for approximately 60
seconds to effect solution.
Add a quantity of dilute mixed
salt solution in accordance
with table 1 of the
Written Standard
that is appropriate to
the range of salt contents
to be measured.
Dilute to 100 milliliters
with mixed alcohol solvent.
Again, shake the
cylinder vigorously
for approximately 30
seconds to effect solution
and allow the solution to stand
for approximately 5 minutes.
Pour the solution into
a dry test beaker.
Immediately place the
electrodes into the solution
in the beaker, making
sure that the upper edge
of the electrode plates
are below the surface
of the solution.
Adjust the indicated electrode
voltage to a series of values--
for example, 25, 50, 125,
200, and 250 volts AC.
At each voltage, note
the current reading
and record the voltage displayed
and the current to the nearest
0.01 milliamperes.
Remove the electrodes
from the solution.
Rinse with xylene, followed by
naphtha, and allow them to dry.
With some apparatus,
the detailed settings
will not be required since
the electrodes are built in
for autoranging.
Determination of the blank and
calibration standard responses
are the same.
Repeat the procedure in section
10.3 of the Written Standard
using other volumes of
mixed salt solution,
dilute solution, as needed to
cover the range of chloride
contents of interest.
Subtract the value obtained
for the blank measurement
from the indicated
current readings
of each standard sample.
And plot the chloride content--
ordinate-- against net
current milliamperes reading--
abscissa-- for each
voltage on a 3-by-3 cycle
log-for-log paper or
other suitable format.