14
A cyanide electrode may be used as an indicator to follow
the progress and detect the endpoint of a complexation
titration of CN
-
with silver nitrate standard. Time must be
allowed for the alkali salt to redissolve and mV to settle.
The end point is reached when the formation of insoluble
silver cyanoargentate precipitates occurs. The electrode can
be used in colored samples, or high or variable ionic strength
samples to increase accuracy of the determination. During
the titration the sensor follows the decrease in cyanide
concentration while small additions of silver nitate titrant
are added. The silver reacts with the cyanide ions forming
a precipitate.
Ag
+
+ 2CN
-
<—>
[Ag(CN)
2
]
-
(soluble)
[Ag(CN)
2
]
-
<—>
Ag
+
2AgCN
(insoluble)
At the stoichiometric end point, a large change in mV
occurs. This technique may be useful in obtaining the actual
value of cyanide standards. Measurements may be
automated by use of the Hanna Titrator HI 901 or titrated
manually.
XIII.
XIII.
XIII.
XIII.
XIII. pH
pH
pH
pH
pH
The HI 4109 and HI 4009 electrodes may be used in
solutions with pH values between 11 and 13. Samples
that fall beyond this range should be adjusted.
XIV. S
XIV. S
XIV. S
XIV. S
XIV. Storage and Care of the HI 4009 and
torage and Care of the HI 4009 and
torage and Care of the HI 4009 and
torage and Care of the HI 4009 and
torage and Care of the HI 4009 and
HI 4109 sensors
HI 4109 sensors
HI 4109 sensors
HI 4109 sensors
HI 4109 sensors
The HI 4009 sensor can be stored in very dilute standards
(<10
-3
M) for short periods of time and should be stored
dry with the protective cap on when not in use.
The model HI 4109 combination electrode can be left in
dilute standards (<10
-3
M) for short time periods.
For long term storage, the electrode should be drained and
washed of salts with distilled or deionized water. Unscrew
the upper cap and move outer sleeve up cable. Wrap the
ceramic junction on the inner stem with Parafilm
®
or other
sealing wrap. Place the protective cap provided over the
Titration