Titrimetric determination of free boric acid and tetrafluoroboric acid in nickel plating baths

Titrimetric determination of free boric acid and tetrafluoroboric acid in nickel plating baths

Summary

This bulletin describes the simultaneous potentiometric titration of free boric acid and free tetrafluoroboric acid in nickel plating baths. After addition of mannitol, the formed mannitol complexes are titrated with sodium hydroxide solution. The determination is carried out directly in the plating bath sample; nickel and other metal ions do not interfere.

Instruments and accessories

• 702 SET/MET Titrino, 716 DMS Titrino, 736 GP Titrino, 751 GPD Titrino or 785 DMP Titrino or 796 Titroprocessor with 700 Dosino or 685 Dosimat

• 2.728.0040 Magnetic Stirrer

• 6.3014.223 Exchange Unit

• 6.0222.100 combined LL pH glass electrode with 6.2104.020 electrode cable

Reagents

Titrant: sodium hydroxide solution, c(NaOH) = 0.1 mol/L (or more diluted) D-Mannitol solution, w(mannitol) = 10% in dist. Water

Analysis

Pipet a defined volume of the sample into a plastic beaker, add 30 mL dist. Water and 10 mL w(mannitol) = 10% and titrate with c(NaOH) = 0.1 mol/L.

Calculation

Two equivalence points are obtained, the first of which corresponds to the HBF4 content and the difference between the second and the first equivalence point to the H₃BO₃ content. 1 mL c(NaOH) = 0.1 mol/L corresponds to 8.781 mg HBF₄ or 6.183 mg H₃BO₃

g/L HBF₄ = EP1 * C01 / C00

g/L H₃BO₃ = (EP2 – EP1) * C02 / C00

EP1 = titrant consumption to reach the first EP in mL

EP2 = titrant consumption to reach the second EP in mL

C00 = sample volume in mL

C01 = 8.781

C02 = 6.183

C00= 0.250

Answer

'fr

736 GP Titrino 04268 736.0011

pHc(init) 3.10 DET pH AB 195

smpl size 0.250 ml

EP1 0.834 ml 4.19

EP2 2.786 ml 8.34

HBF4 29.29 g/l

H3BO3 48.28 g/l

stop V reached

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Literature

Metrohm, Application Bulletin No. 195/2 e