Buchi KjelFlex K-360 User Manual download pdf (Page 17)

3 Technical data

17 KjelFlex K-360 Operation Manual, Version C

3.3 Titration solution

The amount of sample and the concentration of the titrant should be optimized, so that the titrant

volume is between 2 and 18 ml (burette volume: 20 ml).

Table 3-5: Titration solution 1

N-amount N-content Sample size Titrant Titrant concentration Titrant volume

5 mg N 0.5 % N 1 g

0.01 mol/l

17.8 ml

10 mg N 1.0 % N 1 g

0.05 mol/l

7.1 ml

50 mg N 5 % N 0.1 g

0.01 mol/l

17.8 ml

100 mg N 10 % N 1 g

0.25 mol/l

14.3 ml

100 mg N 10 % N 1 g

0.5 mol/l

7.1 ml

200 mg N 20 % N 1 g

0.5 mol/l

14.3 ml

200 mg N 20 % N 1 g

1 mol/l

7.1 ml

Table 3-6: Titration solution 2

P-content P-factor N-content Sample size Titrant Titrant concentration Titrant volume

1 % P 6.25 0.16 % N 2 g

0.01 mol/l

11.42 ml

2 % P 6.25 0.32 % N 1 g

0.01 mol/l

11.42 ml

5 % P 6.25 0.80 % N 2 g

0.1 mol/l

5.71 ml

10 % P 6.25 1.6 % N 2 g

0.1 mol/l

11.42 ml

10 % P 6.25 1.6 % N 2 g

0.25 mol/l

4.57 ml

20 % P 6.25 3.2 % N 2 g

0.25 mol/l

9.14 ml

50 % P 6.25 8.0 % N 2 g

0.5 mol/l

11.42 ml

General recommendation

Hydrochloric acid has the disadvantage of degassing. Therefore Buchi recommends to use sulfuric

acid as titrant.

The correction factor for self prepared solutions is called a titer.

The use of standardized titration solutions make a titer determination unnecessary.

Exact titrant concentration = concentration x titer

The titer of the titrant must be known. In case, it is unknown, it must be determined.

Example: Exact titrant concentration = 0.100 mol/l x 0.998

3.4 Reference substances

Table 3-7: Reference substances

Name Purity % N theoretical

(100 % purity)

Recommended

sample size

Recommended titrant

concentration

Digestion necessary

Ammonium

dihydrogen

phosphate

99.5 12.18 0.8 g c(H

) = 0.25

mol/l

Glycine 99.7 18.66 0.5 g c(H

) = 0.25

mol/l

Yes

Phenylalanine 99.0 8.47 0.9 g c(H

) = 0.25

mol/l

Yes

Ammonium

sulfate

99.5 21.21 0.4 g c(H

) = 0.25

mol/l

1 ... 16 17 18 ... 74

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