Potentiometric Determination of Kappa Number of Paper Pulp

Potentiometric Determination of Kappa Number of Paper Pulp

Equipment
Potentiometer = 751 GPD Titrino / Titroprocessor
Electrodes = 6.0418.120 combined massive Pt electrode; input 1

Reagents
c(1/2Na2S2O3) = 0.2 mol/L; D0

Sample
13 g cellulose pulp
780 mL dist. water
100 mL c(1/5KMnO4) = 0.1 mol/L
100 mL c(1/2H2SO4) = 4 mol/L
20 mL dist. water
35 mL w(KI) = 0.10 (10%)

Remarks
The Kappa number is the consumption of c(1/5KMnO4) = 0.1 mol/L in mL. The results are corrected to the consumption of 50% of thepermanganate solution added.
Determine the dry content of the sample: Dry sample at 105 °C for app. 90 minutes. Calculate the dry content in % and enter it ascalculation value C03.
Weigh in an appropriate amount of sample. Add 780 mL of dist.water and defibrate it with the stirrer. Add the mixture of 100 mLc(1/5KMnO4) = 0.1 mol/L und100 mL c(1/2H2SO4) = 4 mol/L as quickly as possible and rinse with 20 mL dist. water. Add 35 mL w(KI) = 0.10 (10%) after a waiting time of exactly 10 minutes to stop the reaction. Titrate immediately. Treat the blank sample in the same way as above. The waiting time may be programmed in the Titrino; the additions can be carried out automatically using a TIP.

Calculations:

p=(C02-EP1)*C04/C05;1;
KappaNo=RS1*C01*C06/C00/C03;1;

p = consumption of c(1/5KMnO4) = 0.1 mol/L in mL
KappaNo = Kappa number
C01 = factor for correction to a 50 % permanaganate consumption,
see table below (p.e. 59.3 1.020)
C02 = mL of c(1/2Na2S2O3) = 0.2 mol/L consumption of blank sample
C03 = dry content in % (p.e. 21.519)
Titratration of c(1/2Na2S2O3) = 0.2 mol/L (0.2) or percent of permanaganate consumption (0.1)
C06 = factor to compensate for entry of dry content in % (100)

Answer

p= (0.2-19.672) x 0.2 / 0.1 = 59.3
KappaNo= 59.3 x 1.020 x 100 / 13.0051 / 21.519 = 21.6

EP1 = 19.672 mL
C00 = 13.0051 g

C01 can only be entered after the titration, because the p value is necessary. Recalculate and print another full report.
Table for correction of 50% of the permanganate solution:

p…… 0.. …1....... 2 .......3 …...4……. 5……. 6…… 7…… 8….. 9

30 0.958 0.960 0.962 0.964 0.966 0.968 0.970 0.973 0.975 0.977

40 0.979 0.981 0.983 0.985 0.987 0.989 0.991 0.994 0.996 0.998

50 1.000 1.002 1.004 1.006 1.009 1.011 1.013 1.015 1.017 1.019

60 1.022 1.024 1.026 1.028 1.030 1.033 1.035 1.037 1.039 1.042

70 1.044

Literature


• TAPPI T236 os-76
• Metrohn’s Teachware on CD-ROM

Method documentation

'pa
751 GPD Titrino 15215 751.0010
DET U KappaNo
parameters
>titration parameters
meas.pt.density… 4
min.incr. ….10.0 ml
dos.rate max….. ml/min
signal drift ….50 mV/min
equilibr.time …26 s
start V: ….OFF
pause ….0 s
dos.element:…. internal D0
meas.input:… 1
temperature…. 25.0 °C
>stop conditions
stop V:…. abs.
stop V…. 40 ml
stop U ….OFF mV
stop EP… 9
filling rate max…. ml/min
>statistics
status:…. OFF
>evaluation
EPC….. 5
EP recognition: all
fix EP1 at U ….OFF mV
pK/HNP:…. OFF
>preselections
req.ident:…. OFF
req.smpl size: value
activate pulse:…. OFF
------------
'fm
751 GPD Titrino 15215 751.0010
DET U KappaNo
>calculations

p=(C02-EP1)*C04/C05;1;
KappaNo=RS1*C01*C06/C00/C03;1;

C00= 13.0051
C01= 1.020
C02= 49.339
C03= 21.519
C04= 0.2
C05= 0.1
C06= 100
------------
'fr
751 GPD Titrino 15215 751.0010
U(init) 416 mV DET U KappaNo
smpl size ….13.0051 g
EP1…. 19.672 ml ….325 mV
p… 59.3
KappaNo …0.0
stop V reached
============
'cu
751 GPD Titrino 15215 751.0010
start V 0.000 ml DET U KappaNo
5.0 ml/div dU=50.0 mV/div
============
'fr
751 GPD Titrino 15215 751.0010
U(init) 416 mV DET U KappaNo
smpl size ….13.0051 g
EP1 ….19.672 ml ….325 mV
p…. 59.3
KappaNo… 21.6
stop V reached
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