Metrohm 901 Titrando User Manual download pdf (Page 31)

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3 Installation

901 Titrando

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Program the barcode reader in such a way that the ASCII character

02 (STX or Ctrl B) is sent as the first character. This first character is

normally referred to as the "Preamble" or "Prefix Code".

Program the barcode reader in such a way that the ASCII character

04 (EOT or Ctrl D) is sent as the last character. This last character is

normally referred to as the "Postamble", "Record Suffix" or "Postfix

Code".

Exit the programming mode.

3.5 Setting up the titration vessel

3.5.1 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).

Figure 12

Schematic configuration of magnetic stirrer, electrode and

buret tip during a titration. a) stirring direction clockwise, b)

stirring direction counterclockwise.

Magnetic stirrer

Electrode

Buret tip

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Metrohm 901 Titrando User Manual Page 31