Thermo Fisher Scientific Ion Selective Electrodes Silver - Manual (Page 16)

Silver/Silver Sulfide Electrode Instruction Manual
16
5. Add 1 ml of titrant and record the mV reading after stabilization. Repeat this operation
four more times.
6.
Using Gran's Plot paper, plot the values as follows:
a) The horizontal axis is the volume axis. Each major division is equal to 1 ml of titrant
used.
b) The vertical axis is the mV axis. Each major division is equal to 5 mV. The axis
should be scaled so that the mV value obtained after 5 ml of titrant added is near the
top of the graph.
7.
After drawing a straight line through the points, the line should intersect the horizontal axis
at 0 ml. (See Figure 4.)
8.
Measure out 100 ml of the sample into a 150 ml beaker, add 1 ml of low level ISA, place
the beaker on the magnetic stirrer, and begin stirring.
9. Prepare a 10 ml burette with the low level chloride titrant mentioned in Step 3 above.
10. Allow the titrant to run slowly into the sample until the mV reading is near the value
recorded for the first 1 ml increment added in Step 5 above. Record the mV reading and
the total volume added.
11.
Add 1 ml increments of titrant and record the mV reading vs the total volume until the mV
reading approaches the highest mV reading recorded in Step 5 above.
12.
Plot the mV reading vs total volume for all points on the Gran's Plot paper. Draw a straight
line through as many points as possible, extending the line to the horizontal axis. The
volume intercept value is equal to the chloride concentration in ppm.
Indicator Titration
A special method for measuring low level cyanide concentration. The silver/sulfide electrode is
capable of cyanide measurements down to 0.03 ppm.