BEHR InKjel P User manual

142109
InKjel P
Digestion Unit
User‘s Manual

142109
Please read this operating manual carefully before starting use of your new InKjel P digestion unit!
The manual introduces you to the use of the apparatus with clear and simple guidance.
For reasons of safety in use of the system, please follow all safety warnings carefully. These are designated in the
text by a warning symbol .
Additional information, which is useful and important for an understanding of the manner of operation of the
apparatus, is denoted by a stripe in the margin.
We wish you success in the use of the
behr InKjel P digestion unit

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Safety Advice
Danger of burns! The digestion tubes and the heating slot get hot!
Never touch the hot glasses, the sample rack, the heating slot or the exhaust tubes with the bare
hands.
Danger of electric shock!
Always install all cables in such a way that they cannot come into contact with the hot zone of the
heating cavity; they could otherwise smoulder through! Always ensure that no liquids can come
into contact with cable connections or the interior of device! Always withdraw the mains plug
before opening the unit! Repairs on electrical, electronic and mechanical modules of this appli‑
ance may be performed only by authorized specialist staff.
Danger: glass can break and cause injury! In working with glass components, observe all appro‑
priate safety precautions.
Be careful in working with corrosive substances! Follow the safety guidance in the pertinent
Safety Data Sheets.
Hazard from toxic gases!
During the Kjeldahl digestion, vapours of sulfuric acid (and other toxic gases) are set free. They
could harm your health and damage the apparatus and your lab equipment.
When performing digesting operations that can set free toxic or corrosive vapours, always use a
scrubber system! Place the digester and the scrubber in a fume cupboard.
Never operate the digestion unit in wet, humid or explosion‑endangered areas!
Maximum air humidity = 80%
Maximum temperature = 40° C

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Contents
Safety Advice ............................................................................................................................................................. 3
Scope of supply......................................................................................................................................................... 5
Parts List .........................................................................................................................................................................5
Correct use of the InKjel P........................................................................................................................................ 5
Warranty Conditions........................................................................................................................................................5
Overview of the behr InKjel P ........................................................................................................................................6
Setting Up the InKjel P.............................................................................................................................................. 7
Fixing the mounting rack .................................................................................................................................................7
Inserting the Equipment ..................................................................................................................................................7
Connecting to Mains Power ............................................................................................................................................8
Switching the Device On........................................................................................................................................... 9
Using the InKjel P...................................................................................................................................................... 9
The operating unit ...........................................................................................................................................................9
The Start menu............................................................................................................................................................. 10
Configuring the InKjel P to meet your needs ............................................................................................................... 10
Write a heating program............................................................................................................................................... 12
Processing samples ..................................................................................................................................................... 13
Maintenance ............................................................................................................................................................ 16
Cleaning the Exhaust Collector.................................................................................................................................... 16
Changing the Exhaust Collector Tube................................................................................................................... 17
Keep your Device Working Reliably as Long as Possible................................................................................... 19
Do Not Use Damaged Vessels!.................................................................................................................................... 19
Always Use a Scrubber!............................................................................................................................................... 19
Don‘t Leave Any Places Empty!................................................................................................................................... 19
Avoid bumping!............................................................................................................................................................. 20
Foaming ....................................................................................................................................................................... 20
Spare Parts............................................................................................................................................................... 21
Technical Data ......................................................................................................................................................... 22
Customer Service.................................................................................................................................................... 22

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Scope of supply
Please check the contents of the pack for completeness
and freedom from damage immediately upon receipt.
Claims resulting from damage during transportation
which is externally apparent must be lodged immedi-
ately with the carrier (i.e., the post/mail service, the rail-
way administration, the freight organization, etc.) - see
the label on the packaging.
In case of damage which is not apparent from outside
(„concealed transportation damage“), please contact the
behr after-sales service immediately upon discovery of
the damage. The same applies in the case of any other
complaints.
Address:
behr Labor-Technik GmbH
Spangerstrasse 8
D-40599 Düsseldorf, Germany
Telephone: [phone]
Telefax: ([phone]
e-mail: [e-mail]
Parts List
InKjel base unit
Mounting rack
4 knurled screws and 4 washers
Sample rack
Exhaust collector with suction hose
Drip pan
Sample vessels, version-dependent:
6 x 250 ml,
12 x 250 ml,
4 x 500 ml or
4 x 750 ml
Option:
behrosog®acid-fume extractor
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Correct use of the InKjel P
The behr InKjel P digestion unit is used for heating
samples in the appropriate digestion tubes. It is used,
in particular, for quantitation of total nitrogen using the
Kjeldahl digestion method. Only use the appropriate
type of digestion tubes.
Please under all circumstances note and adhere to the
following items, in order to ensure the greatest possible
operating safety and reliability and the longest possible
service-life for your digestion unit:
Always operate the appliance in accordance with
the instructions and data contained in this oper-
ating manual!
Modifications to the appliance will result in forfeit
of any guarantee claims and can result in serious
deficiencies in the unit‘s operating safety and
reliability.
During the Kjeldahl digestion, sulfuric acid
vapours (and other aggressive gases) are set
free. Always operate the appliance with a scrub-
ber system (e. g. behrosog) and place the appli-
ance and the scrubber in a fume cupboard.
Never expose the digestion unit to aggressive
vapours, such as fumes from acids, alkalis or
solvents!
Always operate the behr InKjel P digestion unit under
normal laboratory conditions.
Warranty Conditions
We warrant that all our items are free from defects in
material and workmanship and that they will function
well under the condition that they are handled accord-
ing to the art of the trade. The period of warranty is
one (1) year after the date of delivery. This warranty
does not extend to the breaking of glass parts and
any surface defects which may occur when items are
being used. Our liability under this warranty is lim-
ited to the repair or replacement, at our expense, of
any defective item or part if the damage is due to our
fault. Any further claims, especially for consequential
damages, are excluded. The respective item should
be returned to our factory freight prepaid.
Moreover we refer to our general terms of sale and
delivery resp. to the general terms of delivery and
capacity of the electrical manufacturing industry.
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Overview of the behr InKjel P
Suction hose
Exhaust
collector
Mounting rack
Drip pan
Sample rack
Heating slot with
IR radiators
InKjel
base unit
Control unit Mains switch

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Setting Up the InKjel P
Danger of electric shock!
Always install all cables in such a way that
they cannot come into contact with the hot
zone of the heating cavity; they could oth‑
erwise smoulder through! Always ensure
that no liquids can come into contact with
cable connections or the interior of device!
Always withdraw the mains plug before
opening the unit! Repairs on electrical,
electronic and mechanical modules of
this appliance may be performed only by
authorized specialist staff.
Fixing the mounting rack
Place the base unit on a level horizontal surface in
such a way tha the mounting brackets point to the
rear.
Insert the mounting rack between the mounting
brackets from above. Do not push them down to the
bottom but align the lower edges of the rails with the
lower edges of the mounting brackets.
Place a washer on each of the knurled screws, and
screw the mounting rack to the mounting brackets
with the knurled screws.
Inserting the Equipment
Hang the sample rack into the lower hooks of the
mounting rack.
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Insert the drip pan into the slots in the mounting rack
from the front side. Push the drip pan rearwards as
far as it will go.
Connect the suction hose to the nozzle on the back of
the exhaust collector.
Connect the other end of the suction hose to an
appropriate scrubbe device (e. g. a behrosog scrub-
ber). See also the instruction manual of the scrubber.
Hang the exhaust collector into the upper hooks of
the mounting rack.
Connecting to Mains Power
Make sure that your local mains voltage corresponds
to the voltage specified on the instrument label of
your InKjel P.
Make sure the mains switch on the front of the device
is in 0 position.
Plug the InKjel P power cable into a grounded mains
socket.
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Press button for
Enter
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Switching the Device On
Switch the mains switch on the front of the appliance to
the „I“ position.
The mains switch of the behr InKjel P performs two
functions. It is used, on the one hand, to switch the
unit on and off. There is, in addition, a fuse inte-
grated into the switch.
This fuse functions similarly to a miniature circuit-
breaker (m.c.b.) familiar from your household wiring
system. It interrupts the electrical circuit if an over-
current occurs.
Since it is necessary to pretension a spring for this
safety function, the mains switch on the digestor
requires greater force for switching on than a con-
ventional mains switch.
An initialization message will appear briefly on the
displayl when the unit is switched on. The start menu
appears once the initialization routine has been com-
pleted:
Prog 01/01 ==>>
START EIN
- -
The device is now ready for operation.
Don‘t wonder if the start menu appears in German.
This is the factory setting; you‘ll soon see how to
change it (see pp. 10 / 11).
Using the InKjel P
The operating unit
You can program and operate your behr InKjel P quite
simply using a single button. The principle is the same
in all cases:
The principle remains in all cases the same:
Turning the knob enables you to choose an option. The
currently addressable option is recognized by being
highlighted with light text on a dark background.
The knob may be turned in both directions. In doing this,
you will pass all possible options in the display shown
and will always again find the desired option on contin-
ued turning. Try this for yourself.
The desired option is implemented by pressing on the
knob.
The complete procedure of choosing by turning and
implementing by pressing will henceforth simply be
called “selecting”.
Operating unit

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Configuring the InKjel P to meet your
needs
You can, in fact, use your InKjel P for analyses right
now. You should, however, take a couple of minutes to
perform one or two settings.
These settings can, of course, also be made or modified
at a later time.
This screen will appear when the unit is switched on:
Prog 01/01 ==>>
START EIN
- -
Turn the operating button until the ==>> menu item
is indicated and then press the button. The following
menu will appear:
GERAET
PROGRAMM
<<== zurück
01
Select the Geraet (Device) menu item.
You will then move to a menu consisting of two
pages.
Select the required entry by turning the operating but-
ton if you wish to change a setting. Press the button to
select the entry and set the required value by turning the
button. Store the value by pressing the operating button
again.
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The Start menu
1 If no program is running, but a starting time has been
selected, the starting time is displayed here.
This box is otherwise blank.
2 Start menu item: The temperature program most
recently selected starts if this menu item is selected.
What program this is is1 indicated at bottom left.
3 Preheat ON/OFF menu item: if this item is selected,
the InKjel P will preheat with the heating power that
corresponds to the heating power of the first step of
the heating program currently selected. The menu
item will then change to OFF. Select OFF in order to
switch the heating function off again.
4 The program currently selected, and the program
step reached, are indicated here.
5 Continue menu item: select this menu item to access
other possible settings. You can
- select another program
- write a new program
- configure the unit to your needs
Prog 01/01
14:05
==>>
START ON
- -
2
1
54
3

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First page: Language and time
Selecting the language
UHRZEIT
SPRACHE
<<== ==>>
D
11:20
Three languages are permanently programmed in the
InKjel P : D (German), GB (English), F (French). A fourth
language can be added as an option.
German is the default (ex-works) language. A different
language can be selected using this menu.
Select the Sprache (Language) menu item. The
entry for the language will now appear on a dark
background. Turn the operating button until the
required language appears, and then press the but-
ton.
From this point on, all menus and messages will appear
in the language you have selected.
Setting the time
You should also set the time while you are on this page.
The time is required to permit use of the InKjel P‘s
Autostart function.
Select the Time menu item. The first digit of the
hours will then appear marked.
TIME
LANGUAGE
<<== ==>>
GB
11:20
You can now enter the digits for the time one after the
other. Turn the operating button until the correct digit
appears, and then press it.
If an illogical value is entered, such as “26” for the
hours or “61” for minutes, for example, the unit will
reject the value and instead jump back to the first
digit of the setting.
Use ==>> to move to the next page of this menu.
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Second page: Autostart settings
START TIME
AUTOSTART
<<==
OFF
11:20
The Autostart settings can be selected on this page. You
can, for example, set the unit to preheat at a specified
time or to start a temperature program at a specified
time.
Autostart The following possibilities can be selected
here:
Off - the InKjel P will only start to heat
when a program is started or On is
selected in the Start menu.
On - as soon as it is switched on, the
InKjel P will preheat with the heating
power specified in the first step of the
most recently selected program.
Prg - the InKjel P will start the most
recently selected temperature program at
the Start time.
Tme - at the Start time, the InKjel P will
preheat with the heating power speci-
fied in the first step of the most recently
selected program.
Start time Starting time for Prg and Tme.
The value can be set digit-by-digit, as
described before.
<<== back.
Selecting <<== repeatedly returns the unit to the Start
menu.

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Write a heating program
The InKjel P can be used to write up to 25 different
heating programs.
A program can have up to 20 program steps. For each
step you need to enter two values:
the heating power and
the time for which this heating power is to be
maintained.
When writing a program, always note its purpose
and the settings selected.
Select ==>> in the Start menu
and select Program in the menu which then appears.
DEVICE
PROGRAM
<<==
01
You are now on the first page of the Program menu.
Select the entry box for the Program No.
Select the required Program No. You should select 01
if you have not yet written any other program.
PROG.NUMBER
<<== ==>>
01
Then select ==>>.
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You will now see for every program step a page, on
which you can enter the settings for this step.
TIME
HEAT OUTPUT
Program 01/01
<<== ==>>
025
020
The Program No. and the Program Step No. which you
are currently editing are shown in the top line.
Program 07/05, for example, means the fifth step in
Program No. 07.
In the lines below, specify the values for this program
step:
the Heat output in % of total output (ranging from 1
to 100),
and the Time in minutes.
The unit will then heat at the specified percentage of
total heat output for the time specified.
You can enter the values digit by digit. If you make an
invalid entry (e. g. 150%), the device won’t accept this
entry but jump back to the first digit of this field.
When you have finished entering the data for this pro-
gram step, select ==>> to proceed to the next step.
If you want to check the previous program step again,
select <<==. In the top line you can always see which
program step you are editing.
In this way you can make up a program with up to 20
program steps. Maybe you don’t want that many steps
for this program. In this case, just make sure that in the
steps you are not using the heat output and the time are
set to zero.
When everything is finished, select <<== several times
to go back to the start menu.
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Which program for which kind of samples?
When digesting solid samples, you want to get the
samples boiling soon. When this is achieved, they
should not boil too heavily, or part of the nitrogen might
get lost.
So enter a high value for heat output for the first step.
The time you need to enter for this step will depend on
the kind of sample vessels (250-ml or 500-ml vessels),
on the nature and quantity of your samples and the
catalyst employed.
For the second step, use a heat output value that is just
sufficient to keep the samples boiling for the rest of the
time.
When digesting water or liquid samples, the water
must be evaporated before the sulfuric acid will get boil-
ing and the digestion itself starts.
So for the first program step, enter a high heat output
value and a time sufficient to evaporate the water and
then to get the sulfuric acid boiling.
Again, in the second step, continue heating at a lower
heat output for the rest of the time.
When digesting samples that will release large
quantities of gas, it may be necessary to have the
sample react with the sulfuric acid in the cold at first, or
to heat up slowly and cautiously.
For many kinds of sample materials we have prepared
application sheets we can send you.
Processing samples
Switch the InKjel P on (mains switch on the rear
panel of the unit).
Prog 01/01 ==>>
START ON
- -
If you have selected Prg or Tme for the Autostart func-
tions, the starting time will be shown at the top left; the
target temperature will be shown in this position if the
unit is preheating.
Select program
The most recently selected program is displayed in the
bottom line of the Start menu. Select a different program
if this is not the program you require now:
DEVICE
PROGRAM
<<==
01
Select continue ==>>
PROG.NUMBER
<<== ==>>
01
Select Program
and on the next page Program No.
Select the required Program No.
Return to the Start menu by selecting <<==
repeatedly.
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Preheat digester
Danger of burns! The sample vessels
and the heating cavity get hot!
Never touch the hot glasses, the sample
rack or the body of the heating cavity or the
exhaust collector with the bare hands.
If necessary, preheat the digester.
Prog 01/01 ==>>
START ON
- -
Select the ON menu item in the Start menu.
The device will now start to preheat with the heat output
specified in the first step of the program selected. The
ON menu item changes to OFF.
Prog 01/01 ==>>
OFF
- -
Select OFF if you wish to abort preheating.
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Inserting the samples,starting the program
Danger of burns! The sample vessels
and the heating cavity get hot!
Never touch the hot glasses, the sample
rack or the body of the heating cavity or the
exhaust collector with the bare hands.
Use the handles to insert and remove the
sample rack and the exhaust collector.
If you do not insert the complete set of
sample vessels, the scrubber will just draw
lab air since that’s where it meets the least
resistance. Also, condensate may drip out
in the empty places, producing caustic
fumes and damaging the device. Always
insert the complete set of sample vessels
to make sure scrubbing will work correctly.
Place the sample rack bearing the samples in the
heating cavity.
Put the exhaust collector on top of the sample rack
and switch the exhauster system on.
Select the Start menu item in the Start menu.
The InKjel P will now process the heating program step
by step.
With each step, the display will show the heat output,
the time for this program step and total remaining time.
The number of the program step which is currently
being run is shown at the bottom.
The InKjel P does not react to any operation of the
operating button while a program is running. The
program cannot be interrupted by actuating the oper-
ating button. This is intended to prevent any inadvert-
ent interruption or manipulation of a program while it
is running.
Please use the mains switch on the right of the front
side if you should need to abort a digestion.
A signal is heard, and the heating system switches off,
when the program has been completed.
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Finishing digestion and removal of samples
Danger of burns! The inner zone of the
heating block and the sample vessels get
hot!
Never touch the hot glasses or the area
of the heating block around the mounting
holes with the bare hands. Always remove
the samples from the heating block using
the sample rack and allow them to cool as
described here.
Caution: there are acid condensates in the
exhaust collector. They can burn you and
stain the metal parts of your device.
Wash your hands with water after contact
with the condensate. Insert the drip tray
after inserting the exhaust collector in the
mounting rack.
Grasp the sample rack using the two red handles.
Lift the rack carefully, together with the exhaust col-
lector, and hang it on the lower hooks of the mounting
rack.
Leave the exhaust collector on the sample rack until
the samples have cooled down.
Once the samples have cooled, switch the exhauster
system off.
Remove the exhaust collector from the sample rack
and suspend it in the upper hooks of the mounting
rack.
Insert the drip tray into the mounting rack, into the
slots below the exhaust collector.
The sample rack can now be removed for further
processing of the samples.
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Maintenance
Danger of electric shock!
Always ensure that no liquids can come
into contact with cable connections or the
interior of the unit.
Never attempt to open the unit! Repairs
to electrical equipment may be performed
only by specialist electricians.
Danger: glass can break and cause injury!
In working with glass components, observe
all appropriate safety precautions.
Caution: there are acid condensates in the
exhaust collector. They can burn you and
stain the metal parts of your device.
Wash your hands with water after contact
with the condensate. Insert the drip tray
after inserting the exhaust collector in the
mounting rack.
The housing surface of the InKjel P is low-care and
largely insensitive to acids. Never use abrasive cleaning
agents for cleaning of the front or rear panels.
In the drip pan rests of sulfuric acid will collect that have
condensed in the exhaust collector. Clean the drip pan
in regular intervals.
Cleaning the Exhaust Collector
Danger of injury in case of breakage of
glass! Always adhere to your professional
association's regulations when handling
glass elements!
Caution: there may be sulphuric acid in
the exhaust collector! It might burn you.
Adhere to the current Hazardous Sub‑
stances Ordinance!
If, during a digestion, the exhaust collector has been
contaminated by sample components, you can easily
clean it.
Cautiously lay the exhaust collector upside down,
with the nozzles pointing upwards.
Rinse the nozzles with distilled water.
If need be, gently apply a small bottle brush or a pipe-
cleaner to clean the nozzles.
If necessary, you can dismantle the PTFE plates from
the nozzles for cleaning.
Grasp the plate at the sides and bend it until you can
pull it off the nozzle.
Grasp the plates from the middle of the exhaust coll-
ector; there‘s more room there for your hands than
alongside the housing panel.
After cleaning the plates, put them on the nozzles again,
and bend them back into the proper shape.
The PTFE plates are slightly convex. The convex side
must point downwards, towards the digestion vessel.
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Bend the PTFE plates in order to take them out (and
bend them back in form afterwards!)
Convex side of the
PTFE plate must
point downwards, to
the sample vessel

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Changing the Exhaust
Collector Tube
The exhaust collector of the InKjel P consists of a glass
collector tube that conducts the exhaust gas from the
sample vessels to the suction hose, and the steel hous-
ing. If the glassware part should get broken you need
not replace the exchaust collector as a whole but just
insert a new collector tube.
Danger of injury in case of breakage of
glass! Always adhere to your professional
association's regulations when handling
glass elements! The new collector tube
comes ready with the PTFE plates mounted
already, so do not try to remove the PTFE
plates from the broken tube.
Caution: there may be sulphuric acid in
the exhaust collector! It might burn you.
Adhere to the current Hazardous Sub‑
stances Ordinance!
If it has not yet been done, rinse the exhaust collector
with water to remove any residues of acid.
Pull the suction hose off the nozzle of the exhaust
collector.
Lay the exhaust collector to the edge of the desk so
one of the red handles comes to lie beneath the desk,
but make sure the exhaust collector won‘t slide off the
desk.
The glass collector tube is mounted to the roof of the
housing with two pipe clips. Two pieces of silicone hose
are inserted each between the glass tube and the hous-
ing and between the glass tube and the pipe clips, as
buffers. On unscrewing the four screws holding the pipe
clips, the collector tube gets free.
Unscrew the four screws on the roof of the exhaust
collector.
Take the pipe clips and the silicone buffers off the col-
lector tube.
Carefully take the collector tube out of the housing.
You need to tilt the collector tube to get the suction
nozzle out of the gap of the housing.
Lay two new silicone buffers out in the housing, on
the places where the collector tube is to be held by
the pipe clips. Depending on the size of the collector
tube this may be between the outer or the other two
screwholes.
Insert the new collector tube into the housing in such
a way as for the suction nozzle to go through the gap
of the housing, and lay it on the silicone buffers.
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Lay the other two silicone buffers on top of the collec-
tor tube, in the places where the pipe clips are to be
screwed on.
Insert the pipe clips on top of the new collector tube
in such a way as for the screwholes to fit on the scre-
wholes of the housing.
Screw the pipe clips to the housing again but do not
yet tighten them; first you need to align the new col-
lector tube properly.
Shift the new collector tube in such a way that the
exhaust nozzles have the same distance from the
housing on both sides.
Now screw the pipe clips tight.
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Keep your Device Working
Reliably as Long as Possible
The Kjeldahl digestion produces a highly aggres-
sive mixture of sulfuric acid vapour, sulfur dioxide and
organic vapours. This gas mixture will, with time, cor-
rode even stainless steel surfaces and make them look
shabby.
Do Not Use Damaged Vessels!
Before preparing the samples, check the sample ves-
sels. Do not use vessels that have a fissure; they might
burst when heated.
Always Use a Scrubber!
The exhaust gases coming out of a Kjeldahl digestion
are corrosive; moreover they are poisonous, and they
will also damage your lab equipment. So always use a
scrubber system, as e. g. the behrosog 3. Fill the gas
washing flasks according to the user’s manual (the first
one with water, the second one with diluted NaOH).
Connect the suction hose to the outlet nozzle in the rear
of the exhaust collector.
Make sure to insert the exhaust collector properly on the
sample vessels. The suction nozzles must reach into
the vessels; the uppermost disk on the nozzles will rest
on the rim of the vessel. Adjust the suction flow rate in
such a way that the white fumes are sucked off but no
vacuum will arise.
Don‘t Leave Any Places Empty!
The suction air current will always go the way of least
resistance. So if you leave some sample places empty,
if there is no sample vessel under the suction nozzle,
the scrubber will aspirate most of its air from there.
The caustic vapours coming out of the samples are not
removed; instead, they will creep over the rim of the
vessel. Caustic condensate may drip down from there,
damaging the heating block and the sample rack. If
worst comes to worst, drops may come into the gap
between the vessel and the boring in the heating block,
evaporating explosively and cracking the vessel. So
always insert samples on all sample places; at least,
insert empty sample vessels.
Never use vessels that have
fissures
PTFE disk must cover the
mouth of the sample vessel
Samples in all
places:
Waste gas will be
removed smoothly
Some places left free:
Scrubber will draw air,
gas will accumulate and
come out sideways
Condensate can
drip down and
corrode your device

– 20 –
behr InKjel P
142109
Avoid bumping!
With liquid samples, bumping may occur so that liquid
will splash out of the sample. With liquid samples, add
some boiling chips. Boiling chips do not contain nitro-
gen. Nevertheless, treat the blank in the same way as
the samples.
When digesting liquids like water or milk, the water con-
tained in them must be evaporated before digesxtion
really starts. During this time, heating must be adjusted
in such a way that the sample is boiling steadily but
does not boil over.
Foaming
Some kinds of samples will develop a foam when react-
ing with concentrated sulfuric acid, which will rise up in
the vessels, creep over the rims or even rise into the
suction nozzles. Textbooks have various advices what
to do against foam – but it will depend on the kind of
sample which technique will work.
Heating slowly so the foam won’t rise so fast, maybe
even preparing the sample in the evening and letting
it rest overnight before starting the digestion. That
will sometimes work, but it won’t always work. Some
sample materials will start reacting with the sulfuric
acid in the cold, and the longer it takes the sample to
reach digestion temperature, the higher the foam will
rise.
In these cases it is better to have the sample come
to digestion temperature as quick as possible so the
foam will collapse soon. Which means: preheat the
block and prepare the sample immediately before
starting the digestion.
An anti-foam agent can neutralize the foaming com-
ponents of the sample. Add some drops of paraffine
oil or silicone oil to the sample. Make sure to treat
the blank in the same way as the samples.
If you have an infrared digestion device (e.g. behr
InKjel) too, the easiest way to digest high-protein
samples will be the infrared digestion. In an infrared
digestion, the samples reach digestion temperature
very quickly so the foam will collapse soon.
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For liquid samples,
use boiling chips