Metrohm 905 Titrando - Manual (Page 36)

4.1 General
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905 Titrando
4 Setting up the titration vessel
4.1 General
During the titration, it is important that the solution be well-mixed. The
stirring rate should be high enough for a small "vortex" to appear. If the
stirring rate is too high, then air bubbles will be aspirated. This results in
incorrect measured values. If the stirring rate is too low, then the solution
at the electrode will not be correctly mixed. In order to ensure that mea-
surement is carried out in a well-mixed solution following addition of the
titrant, the buret tip should be placed in a position where the turbulence is
high. In addition, the distance between the addition of the titrant and the
electrode should be as large as possible. Also take into account the stirring
direction (counterclockwise or clockwise) when positioning electrode and
buret tip (see figure below).
1
2
3
1
2
3
a) b)
Figure 18 Schematic configuration of magnetic stirrer, electrode and
buret tip during a titration. a) stirring direction clockwise, b)
stirring direction counterclockwise.
1 Magnetic stirrer 2 Electrode
3 Buret tip