User Manual

NORMAL OPERATION
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9. Allow tubes to cool for 5-8 minutes. Dilute digest with approximately 100-ml water
when tubes are cool enough to handle. Dilution must be made before a cake is
formed from precipitated salts, but not before the digest is cool enough to contain the
exothermic reaction. (The cooling period is very important since, in the
determination procedure, caking of the salts will cause low recoveries of the nitrogen
contained in the cake.
10. After dilution of the digested sample, the nitrogen content can be determined by
Labconco’s Rapid Distillation Apparatus, normal Kjeldahl distillation, specific ion
electrode, steam distillation, or by manual or automated colorimetric determinations.
The general method presented for the digestion of total Kjeldahl nitrogen is a basic
method being used in many laboratories doing feeds and grain digestions.