7 Maintenance
K-375 / K-376 / K-377
Operation Manual, Version E
142
Inorganic substances
Several minutes, e. g. with
HCl 0.1 mol/L or NaOH 0.1
mol/L
Improved cleaning action with
warm solutions (40–50 °C)
Organic substances
(oil, grease, etc.)
Rinse off with a suitable organic
solvent (e.g. ethanol) or tenside
solution
For plastic shaft electrodes,
take chemical resistance into
account. Sensor can also be
wiped off with a soft, moistened
cloth.
Proteins
Approx. 1 hour with pepsin/HCl
solution
5 % pepsin in 0.1 mol/L HCl
Sulfides (on ceramic
diaphragm)
With thiourea/HCl solution
(6.5 % in HCl 0.1 mol/L ) up to
discoloration
Cause: Reaction of electrolyte
with measuring solution.
Table 7-1: Cleaning methods of the pH electrode
7 7 3
Replacing the buret
As a rule, the need for replacing the buret occurs only rarely. It has to be replaced only as a result of a
defect.
7 7 4
Cleaning the splash protector and the rubber seal
In case the splash protector or the rubber seal is contaminated and this contamination was not
removed during the daily maintenance work, proceed as follows:
∙ Dismount the splash protector and remove the rubber seal.
∙ Rinse the splash protector with water to remove sample residues.
We recommend to replace the glass splash protector after approximately 3000 – 5000 determi-
nations, depending on the kind of application and frequency of maintenance. The plastic splash
protector can last more than 8000 distillations.
To prolong the lifetime of the seal, rinse it with water, especially if working with crystalline products.
Afterwards, dry it with a soft cloth, remount it and put the splash protector back in place.
NOTICE
Risk of device damage.
∙ When removing and reinstalling the seal, make sure not to damage it.
∙ Always move it perpendicularly to the axis of the glass parts and ensure no
damage occurs to the sealing lip.
∙ Never apply grease to the seal and never touch it with sharp objects, otherwise
it will get damaged.
7 7 5
Glass parts
Replace the sample tubes and the condenser if broken (see chapter 7.3.5). In case a KjelSampler
K-376 / K-377 is used, the 500 mL tube, used for all distillations, should be replaced whenever a new
splash protector is mounted to the K-375.