Buchi KjelSampler K-377 Manuel d'utilisateur télécharger pdf (Page 37)

4 Description of function

K-375/376/377 Operation Manual, Version B

4.5.5 Measuring Mode

Startpoint pH

The device measures the pH of the boric acid before the distillation is started and uses it later on as

enpoint for the titration. If the boric acid used as receiving solution is not adjusted to pH 4.65 the

startpoint mode is recommended.

Endpoint pH

The set value, normally 4.65, is used as endpoint for the titration. The boric acid has to be adjusted

to pH 4.65 before starting sample measurements. This mode is more accurate and yields the highest

accuracy.

4.5.6 Titration Algorithm

Normal

This algorithm is the most accurate one and is recommended for samples with low nitrogen content

(below 1 mg) and for the use of highly-concentrated titration solutions (e.g. 0.5 N acids).

Optimal

The best ratio between accuracy and process speed is achieved with this algorithm.

4.5.7 Determination Mode

Standard

In the majority of cases it is necessary to digest samples to make the nitrogen accessible to steam

distillation. Whenever digested samples are analyzed the standard determination mode is used.

Direct Distillation

A small number of applications allow freeing the nitrogen via direct steam distillation without requiring

a digestion. In such a case the direct distillation mode needs to be activated.

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Buchi KjelSampler K-377 Manuel d'utilisateur Page 37