Stirring, Purging, Stirring purging – Metrohm 797 VA Computrace User Manual

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3.4 General operation sequence

797 VA Computrace – Software

urement)

is not checked, the stirrer is switched off during that

time

(details see Pretreatment).

9. Voltage sweep

Start of the voltage sweep which depends on the selected
measurement mode (details see VA measurement modes, sec-
tion 3.2).

10. Stand-by potential

Optional apply of a

Stand-by potential

before the start and af-

ter the end

of the voltage sweep (details see Stand-by poten-

tial).

Note: If you work with the electroplating bath modes CVS and
CPVS, the operation sequence is different (see section 8.6 Operate
a sequence in Electroplating Bath VA)

Stirring

If switched on (

Stirrer > 0 rpm

), the solution in the sample vessel at

the 797 VA Computrace stand is stirred during all preparation pro-
cedure steps until the start of the equilibration time.

Exception: Hydrodynamic measurements in the CV mode, where
the stirring continues during measurement.

Stirrer (rpm)

[ 0...3000 rpm ; 2000 rpm ]

Revolutions per minute of the stirrer.

Purging

Purging means saturation of the analysis solution with an inert gas
and is used to remove the electrochemically active and hence inter-
fering oxygen. With the inert gas flow rate of ca. 20 l/h set on the
797 VA Computrace stand, a purging time of ca. 3...5 min. usually
suffices. For an effective purging of the analysis solution, the solu-
tion should also be stirred.

Initial purge time (s)

[ 0...80600 s ; 300 s ]

(

Initial mixing time

with

CVS and CPVS, see section 6.3

Initial mixing time with CVS

and CPVS

)