Labconco Rapid Distillation Apparatus 65000 - Manual (Page 11)

NORMAL OPERATION
7
Samples Digested Utilizing Micro-Digestor –
Start-up and Operation
The Labconco Rapid Distillation Apparatus is designed to conform with standard Micro
Kjeldahl distillation techniques. The preparation of digested samples, chemical treatment of the
sample prior to distillation and titration techniques following the distillation are adequately
described in A.O.A.C. Methods of Analysis and other technical references, and should be referred
to in ALL cases.
(1)
Turn on cooling water and adjust to normal rate.
(2)
Turn on heater – check reservoir level and adjust to 2/3 full if required. Set heat control at
“9” on the dial. Allow steam reservoir water to come to “boiling” and turn down heat
control to proper setting. Adjust flow control valve to replace water lost during distillation.
(3)
Allow still to reach thermal equilibrium – check for 4-5ml/min. distilling rate, with small
graduate (refer to Step 8 of Start-up and Check Out).
(4)
Open aspirator stopcock joining still chamber and water aspirator aspirate inner chamber –
close the stopcock.
(5)
Place a receiver flask, containing a volume of receiving solution on shelf at outlet of
condenser.
(6)
Check stopcock on sample addition funnel to see that it is closed. Place entire diluted
digest sample in addition funnel.
(7)
Open “addition” funnel stopcock to transfer digest sample to the mixing chamber. Close
stopcock.
(8)
Rinse digestion flask with several small amounts of ammonia-free distilled water (total
volume of rinses not to exceed 8 to 10 ml). Adding each small rinse to the inner chamber
through the addition funnel separately and closing stopcock after each addition.
(9)
Rinse addition funnel with 3 to 4 ml ammonia-free distilled water, leaving some water as a
liquid seal.
(10) Raise receiver flask shelf, positioning it so that the condensate outlet is slightly below the
receiving liquid surface level.
(11) Add strong alkali solution (calculated to produce excess base in mixing chamber when
completely added) to addition funnel. Open funnel SLOWLY and allow alkali to slowly
flow into the mixing chamber. Stop flow if “neutralizing action” becomes too vigorous or
siphon back of receiving solution. Continue intermittent feeding of alkali to mixing