4 Description of function
K-375 / K-376 / K-377
Operation Manual, Version E
36
4.5 Distillation and titration
4 5 1
Distillation and Titration Options
Titration
type
Titration
mode
Distallation
mode
Measuring mode
Titration
algorithm
Boric acid
Back titration
Standar
d
Online
IntelliDist
Fixed time
Endpoint pH
Startpoint pH
Setpoint mV
Optimal
Normal
Potentiometric
x
x
x
x
x
x
x
x
x
x
Colorimetric
x
x
x
x
x
x
x
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Distillation Mode
Automatic – IntelliDist
This mode eliminates errors caused by a cooled instrument. The countdown of the set distillation time
only starts after operating temperature is attained. With single samples or sample list measurements
this mode guarantees result accuracy from the very first run.
Fixed Time
The countdown of the set distillation time starts immediately with the start of the distillation process.
This setting is recommended when a sample changer is used for the analysis of samples in a rack (or
sequence).
4 5 3
Titration Type
The built-in titrator is fully controlled via the K-375 software. It is not possible to use the titrator without
the KjelMaster K-375. It can be used for boric acid or back titration. The measuring mode can be
determined as endpoint or startpoint titration by defining the method in the K-375. The software of the
K-375 allows to choose between standard and online titratio
n.
Boric Acid Titration
Boric acid adjusted to a pH of 4.65 is used as receiving solution to capture the nitrogen carried over
as ammonia during the steam distillation. The subsequent endpoint titration (pH 4.65) is performed
with an acid titration solution. This titration type does not require an accurate dosage of the boric
acid.
Back Titration
The receiving solution is a standardized acid (e.g. H
2
SO
4
) of which an accurate volume is dispensed
into the receiving vessel. After collecting the ammonia the excess acid is titrated with a basic titration
solution (NaOH) at pH 7.00. If the use of boric acid has to be avoided the back titration is the proce-
dure of choice.
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Sensor Type
Potentiometric
Potentiometric pH measurement is
commonly used and allows
both boric acid and back titrations.
They need regular calibration with buffers.
Colorimetric
Colorimetric titration is based on colour change at the equivalence point and is used in situations
where an official standard requires it. For sound measurements and reproducible results the conden-
sate outlet with air bubble trap must be fitted. The condensate outlet prevents air bubbles interfering