Hanna Instruments HI 904 - Manual (Page 85)

6-3
TITRATION
6 TITRATION
6.1 Idle
The titrator first enters Idle mode when it is switched on. All of the HI 904’s software features
and adjustable parameters can be accessed from the Idle state. This includes all of the
user-adjustable method parameters, solvent handling system, file transfers, calibration checks,
software upgrades, options for interface with PC and accessories as well as burette options.
To access the titration menu ( Process screen) press .
The titration is performed with the selected method.
Be sure that the selected method is customized in accordance with the specifics of the application.
Before performing a titration, make sure that the following conditions are met:
• All of the attached systems (e.g.: reagent system) are properly assembled.
• The right amount of reagent is present in the titration vessel (between the min and
max marks) for best reproducibility.
The following intermediary stages are performed automatically before starting the analysis:
• Reagent pre-titration
• Drift analysis (
Automatic Drift Entry / KF Coulometric only)
When the drift analysis process is finished, the titrator enters Standby mode. At this point,
a titration can be initiated.
6.2 Pre-titration
In pre-titration, the residual water on the interior surface of the titration vessel, the water
contained in the entrapped air and the small amount of water from the reagent, is elimi-
nated. The HI 904 reacts residual water with iodine that is generated electrolytically inside
the titration vessel until the specified end point potential is reached; this setting is associated
with the active method. After the electrode potential has stabilized, the titrator moves into
the Drift Rate Determination Stage.
When the pre-titration is started, the stirrer is automatically turned on (when
Internal or
External stirrer is selected).