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© behr Labor-Technik 2013
249101
Checking the Reagents Pumps
The steam distiller S 5 doses reagents into the sample
vessel and into the titration vessel automatically:
Dilution water into the sample vessel
Sodium hydroxide into the sample vessel
Boric acid into the titration vessel.
The quantities delivered need not be stoichiometric (and
neither are the reagents volumetric solutions); they just
have to fulfill their purpose:
Diluting water must be sufficient so the reaction
when sodium hydroxide is added won’t get too vio-
lent
Sodium hydroxide must be sufficient to make the
sample alkaline so all of the ammonia will be distilled
Boric acid must be sufficient to trap the NH
3
that has
been distilled.
Titration goes to the pH of the original boric acid. So
the boric acid solution, too, need not be furnished in
an exactly measured quantity; it must be sufficient but
should not dilute the distillate unnecessarily.
The quantities to be delivered result from the running
times of the pumps. When creating a distillation pro-
gram, you enter pump running times in seconds. Pages
14 - 15 tell which running times will approximately result
in which deliveries. You can easily check the pump
deliveries yourself; for this, there are the test programs
90 through 92:
Program 90 for the boric-acid pump
Program 91 for the diluting-water pump
Program 92 for the sodium hydroxide pump.
The viscosity of the chemicals - especially of the
sodium hydroxide solution - is different from the vis-
cosity of water. Check pump deliveries with the same
chemicals that are to be dosed with these pumps to
be sure that the delivery rates in a real distillation will
be the same as in the test.
Risk of burns and injuries! When work-
ing with corrosive substances, follow the
safety guidance in the pertinent Safety
Data Sheets.
Deliveries will depend somewhat on the conditions
in your lab (length of hose lines, chemical vessels
placed on the floor or on the desk).
Checking the Diluting Water Pump
Select Destillation program # 91.
Insert an empty sample vessel into the mounting.
Close the door of the device.
Start the test program and wait till it is finished.
A message will appear telling you to start manual
titration. Just turn the control knob to confirm you’re
ready.
Take the sample vessel out and pour the contents
into a graduated cylinder (100 ml).
In 5 seconds, the diluting water pump should deliver
approximately 70 ml.
Checking the Sodium Hydroxide Pump
Select Destillation program # 92.
Insert an empty sample vessel into the mounting.
Close the door of the device.
Start the test program and wait till it is finished.
A message will appear telling you to start manual
titration. Just turn the control knob to confirm you’re
ready.
Take the sample vessel out and pour the contents
into a graduated cylinder (100 ml).
In 5 seconds, the sodium hydroxide pump should deliver
approximately 50 ml if the NaOH vessel is placedon
the floor (it may be as much as 70 ml if the vessel is
placed on the lab desk).
Checking the Boric Acid Pump
Pull the boric acid hose out of the titration vessel and
lead it into an empty graduated cylinder of 100 ml.
Start the test program and wait till it is finished.
A message will appear telling you to start manual
titration. Just turn the control knob to confirm you’re
ready.
Read the liquid level of the graduated cylinder.
In 5 seconds, the boric acid pump should deliver
approximately 70 ml.
If the delivery of a pump differs very much, check if the
connections are leaky or if the hoses are clogged or
kinked. If the cause cannot be located there, the pump
might be defective.
Cleaning the NaOH Lines
During use of the distiller, soda (Na
2
CO
3
) can form
from the sodium hydroxid and form deposits in hoses,
non-return valve and pump. We recommend, therefore,
to rinse the NaOH lines with diluted hydrochloric acid
every 3 months to dissolve any such deposits.
Rinse the lines with water as described before. Stay
in the Manual entry menu.
Pour 100 ml diluted hydrochloric acid (about 5%) into
a suitable vessel and insert the NaOH suction lance.
Select NaOH and keep the control knob pressed until
the hydrochloric acid has just been sucked in.
Let the acid work for some minutes.
Pour distilled water into the vessel and rinse the lines
with it. To rinse thoroughly, use at least 300 ml water;
empty the sample vessel when it is full, re-insert it
and continue rinsing.
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