Potentiometric Determination of the White Liquor

Potentiometric Determination of the White Liquor

Equipment
Potentiometer = 751 GPD Titrino / Titroprocessor
Electrodes = 6.0239.100 combined pH glass electrode; input 1

Reagents
c(HCl) = 1 mol/L; D0

Sample
2.00 mL white liquor
white liquor is a mixture of NaOH, Na2S (pK1=7.04,pK2=11.96), Na2CO3 (pK1=6.37, pK2=10.25)
50 mL dist. Water

Remarks
Pass a stream of nitrogen through the solution during titration.
1st break: OH- + S-- + 2 H+ H2O + HS-
2nd break: CO3-- + H+HCO3-
3rd break: HCO3 + HS- + 2 H+ H2CO3 + H2S

Calculations:

Total=EP3*C01*C02/C00;2;g/l
Active=(EP3-C03*(EP2-EP1))*C01*C02/C00;2;g/l
Effecti.=EP1*C01*C02/C00;2;g/l
NaOH=(EP1-((EP3-EP2)-(EP2-EP1)))*C01*C02/C00;2;g/l
Na2S=((EP3-EP2)-(EP2-EP1))*C03*C02*C04/C00;2;g/l
Na2CO3=(EP2-EP1)*C03*C02*C05/C00;2;g/l

Total = total alkali (NaOH + Na2S + Na2CO3) as g NaOH per liter
Active = active alkali (NaOH + Na2S) as g NaOH per liter
Effecti. = effective alkali (NaOH + ½ Na2S) as g NaOH per liter
NaOH = concentration of NaOH in g/L
Na₂S = concentration of Na2S in g/L
Na₂CO₃ = concentration of Na2CO3 in g/L
C01 = molecular mass of NaOH (40 g/mol)
C02 = concentration of titrating agent (1 mol/L)
C03 = factor (2)
C04 = molecular mass of ½ Na2S (39 g/mol)
C05 = molecular mass of ½ Na2CO3 (53 g/mol)

Answer

Tota l= 7.625 x 40 x 1 / 2.00 = 152.50 g/L
Active = ( 7.625-2(6.081-5.714)) x 40 x 1 / 2.00 = 137.82 g/L
Effecti.= 5.714 x 40 x 1 / 2.00 = 114.28 g/L
NaOH=(5.714-((7.625-6.081)-(6.081-5.714)))x40x1 / 2.00 = 90.74 g/L
Na2S= ((7.625-6.081)-(6.081-5.714)) x 2 x 1 x 39 / 2.00 = 45.91 g/L
Na2CO3= (6.081-5.714) x 2 x 1 x 53 / 2.00 = 19.45 g/L

EP1 = 5.714
EP2 = 6.081
EP3 = 7.625

Literature
SCAN - N2:63 (1963)

Method documentation

'pa
751 GPD Titrino 15215 751.0010
DET pH W-Liquor
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 ….9 ml
stop pH ….OFF
stop EP ….9
filling rate max….. ml/min
>statistics
status:…. OFF
>evaluation
EPC ….5
EP recognition:…. all
fix EP1 at pH…. OFF
pK/HNP: ….OFF
>preselections
req.ident: ….OFF
req.smpl size:…. OFF
activate pulse: ….OFF
------------
'fm
751 GPD Titrino 15215 751.0010
DET pH W-Liquor
>calculations
Total=EP3*C01*C02/C00;2;g/l
Active=(EP3-C03*(EP2-EP1))*C01*C02/C00;2;g/l
Effecti.=EP1*C01*C02/C00;2;g/l
NaOH=(EP1-((EP3-EP2)-(EP2-EP1)))*C01*C02/C00;2;g/l
Na2S=((EP3-EP2)-(EP2-EP1))*C03*C02*C04/C00;2;g/l
Na2CO3=(EP2-EP1)*C03*C02*C05/C00;2;g/l

C00= 2.0
C01= 40
C02= 1
C03= 2
C04= 39
C05= 53
------------
'fr
751 GPD Titrino 15215 751.0010
pHc(init) 12.85 DET pH W-Liquor
smpl size…. 2.0 ml
EP1 …..5.714 ml …10.76 mV
EP2 …..6.081 ml….. 8.67 mV
EP3 …..7.625 ml….. 4.09 mV
Total …152.50 g/l
Active ..137.82 g/l
Effecti. …114.28 g/l
NaOH ….90.74 g/l
Na2S …45.91 g/l
Na2CO3 …19.45 g/l
stop V reached
============
'cu
751 GPD Titrino 15215 751.0010
start V 0.000 ml DET pH W-Liquor
1.0 ml/div dpH=2.0/div