Labconco Rapid Distillation Apparatus 65000 - Manual (Page 13)

NORMAL OPERATION
9
Samples Digested Utilizing Rapid Digestor –
Start-up and Operation
Same as information under Samples Digested Utilizing Micro-Digester.
Principle
(1)
After sample digestion, utilizing the Labconco Rapid Digestor-4, Rapid Digestor-25, or
equivalent digestion apparatus, a portion of the sample is transferred to the Rapid
Distillation Apparatus. Ammonia is steam distilled into standard acid and back titrated
with standard alkali. Complete recovery of nitrogen is accomplished in 3 – 5 minutes
distillation time.
Apparatus
(1)
Labconco Rapid Distillation Apparatus Model 65000. Available from Labconco
Corporation, 8811 Prospect Avenue, Kansas City, MO 64132.
(2)
Erlenmeyer Flasks. 125 ml Erlenmeyer flasks for standard acid receiving solution.
(3)
Pipets. 20 ml volumetric pipets for sample transfer.
(4)
Burets. 15 ml buret for standard acid and standard alkali. Separate burets should be used
for the addition of the acid and alkali.
Reagents
(1)
Sodium hydroxide/potassium sulfide. Dissolve 45g solid NaOH in water. While still
warm, dissolve 10g of K
2
S in the NaOH solution, cool and dilute to 1 liter.
(2)
Methyl red indicator. Dissolve 1g methyl red in 200 ml ethyl alcohol.
(3)
Sodium hydroxide standard solution. 0.01N, prepare as in AOAC Official Methods of
Analysis, Thirteenth Edition, p. 877.
(4)
Sulfuric acid standard solution. 0.05N, prepare as in AOAC Official Methods of Analysis,
Thirteenth Edition, p. 877.
Standardize each standard solution with primary standard and check one against the other.
Refer to AOAC Official Methods of Analysis, Thirteenth Edition, Chapter 50. Test all reagents
before use by blank determination with 1g sugar.