Gerhardt Vapodest 45s - Page 32

31
Vapodest 45s
7 Create a method (Programming)
M01 Adding H2O
100ml
turn
press
press
M01 Adding NaOH
80ml
turn
press
press
3. Addition H
2
O
A sufcient dilution of the concentrated sulphuric
acid reduces the energy which is set free during
the alkalinisation process. The addition of H
2
O
depends on the amount of the free (unbound)
sulphuric acid at the end of the digestion.
In general the 5fold amount of water is sufcient.
- Setting range 0 - 200 ml
(the specication of the dosing steps depends on
the calibration of the pumps).
4. Addition NaOH
In order to be able to distil ammonia over it is im-
portant to create a strong alkaline environment.
When catalysts containing copper sulphate are
used, a colour change of the sample takes place
if it is alkaline. When Selen is used as a catalyst,
an indicator can be added to the sample to have
a visual check. The addition of NaOH depends on
the amount of free (unbound) sulphuric acid at the
end of the digestion.
In general, the quadruple amount is needed for a
32% NaOH.
- Setting range 0 - 200 ml
(the specication of the dosing steps depends on
the calibration of the pumps).
5. Reaction time
The reaction time is especially for the nitrate nitro-
gen determination when Devarda’s alloy is used
(e.g. for the analysis of fertilizers). For Kjeldahl
analysis this amount of time is not necessary.
- Setting range 0 - 99 min and 0 - 59 s
M01 Reaction
00min 00s
turn
press
press
BeiPlease note!
When using the Vap
45s without titrator,the
addition of H
3
BO
3
is
programmed here,
also see step 10.