BUCHI KjelFlex K-360 - Manual (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 H
2
SO
4
0.01 mol/l 17.8 ml
10 mg N 1.0 % N 1 g H
2
SO
4
0.05 mol/l 7.1 ml
50 mg N 5 % N 0.1 g H
2
SO
4
0.01 mol/l 17.8 ml
100 mg N 10 % N 1 g H
2
SO
4
0.25 mol/l 14.3 ml
100 mg N 10 % N 1 g H
2
SO
4
0.5 mol/l 7.1 ml
200 mg N 20 % N 1 g H
2
SO
4
0.5 mol/l 14.3 ml
200 mg N 20 % N 1 g H
2
SO
4
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 H
2
SO
4
0.01 mol/l 11.42 ml
2 % P 6.25 0.32 % N 1 g H
2
SO
4
0.01 mol/l 11.42 ml
5 % P 6.25 0.80 % N 2 g H
2
SO
4
0.1 mol/l 5.71 ml
10 % P 6.25 1.6 % N 2 g H
2
SO
4
0.1 mol/l 11.42 ml
10 % P 6.25 1.6 % N 2 g H
2
SO
4
0.25 mol/l 4.57 ml
20 % P 6.25 3.2 % N 2 g H
2
SO
4
0.25 mol/l 9.14 ml
50 % P 6.25 8.0 % N 2 g H
2
SO
4
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
2
SO
4
) = 0.25
mol/l
No
Glycine 99.7 18.66 0.5 g c(H
2
SO
4
) = 0.25
mol/l
Yes
Phenylalanine 99.0 8.47 0.9 g c(H
2
SO
4
) = 0.25
mol/l
Yes
Ammonium
sulfate 99.5 21.21 0.4 g c(H
2
SO
4
) = 0.25
mol/l
No