Potentiometric Determination of Pure Silver Content

Potentiometric Determination of Pure Silver Content

Equipment
Potentiometer = 751 GPD Titrino / Titroprocessor
Electrodes = 6.0404.100 combined massive Ag electrode with AgBr coating; input 1

Reagents
c(KBr) = 0.1 mol/L; D0

Sample
app. 250 mg Ag
10 mL HNO3 65 %
100 mL dist. water

Remarks
Calculations:

Silver=EP1*C01*C02*C03*C04/C00;3;%

Silver = content of silver in % ( purity )
C01 = concentration of titrating agent (0.1 mol/L)
C02 = titer (1.0)
C03 = molecular mass of Ag (107.87 g/mol)
C04 = factor for % (100)

Answer

Silver = 22.332 x 0.1 x 1.0 x 107.87 x 100 / 257.7 =93.479 %

EP1 = 22.332 mL
C00 = 257.7 mg

Sample preparation:
Heat silver in HNO3. Allow nitrous fumes to evaporate.

AgBr coating of electrode:
Clean Ag electrode with scouring agent and electrolyse in (HBr) = 0.1 (10%) during 2 h with 5 mA using a 6.0305.000 Pt lectrode as cathode. Stir during electrolysis.

Literature
Metrohm Application Bulletin No. 61: Potentiometric determination of silver.

Method documentation

'pa
751 GPD Titrino 15215 751.0010
DET U…. Silver
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: …..abs.
start V …..17 ml
dos.rate max….. ml/min
pause ….0 s
dos.element:…. internal D0
meas.input: ….1
temperature ….25.0 °C
>stop conditions
stop V: ….abs.
stop V ….24 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:…. all
activate pulse: ….OFF
------------
'fm
751 GPD Titrino 15215 751.0010
DET U…. Silver
>calculations

Silver=EP1*C01*C02*C03*C04/C00;3;%

C00= 257.7
C01= 0.1
C02= 1.0
C03= 107.87
C04= 100
------------
'fr
751 GPD Titrino 15215 751.0010
U(init) 280 mV DET U Silver
smpl size …..257.7 mg
EP1 ….22.332 ml ……30 mV
Silver …..93.479 %
stop V reached
============
'cu
751 GPD Titrino 15215 751.0010
start V 17.000 ml DET U Silver
1.0 ml/div dU=100.0 mV/div