The authoritative public forum
  for Metal Finishing since 1989
-----

Gravimetric determination of sulphate in Cr(III) solution

 

Hello!

Does anyone know a gravimetric method for determination of sulphate in a solution containing approximately 0.5 M Cr(III)? The acidity of the solution is very low (pH<1)and I have tried to precipitate the sulphate as BaSO4 by adding excess (10 ml 10%) BaCl2. However, this hasn't worked. Can anyone tell me what I am doing wrong?

Thank you,

Krister Backlund
- Turku, Finland

---

 

1. Make a solution containing 15 parts isopropyl alcohol, 7 parts HCl, 25 parts glacial acetic acid ⇦this on eBay or Amazon [affil links] .
2. Pipette [pipettes on eBay or Amazon [affil links] 10 ml plating bath into a 400 ml flask. Add 75 ml of the solution from step 1 and boil in a hood for 15-20 minutes.
3. Add 50 ml hot di water and 5 ml of 30% BaCl solution
4. Add 5 ml saturated picric acid solution and let stand for 2 hours.
5. Filter through a preweighed grooch crucible.
6. Dry at 120C to a constant weight.

Weight of filtrate (g) x 42.02 = g/L H2SO4

James Totter, CEF
- Tallahassee, Florida

---

JIM,

PICRIC ACID HAS BEEN REMOVED, THEN BANNED FROM THE CABINETS OF LABORATORIES SINCE THE LATE 1970'S BECAUSE IT FORMS EXPLOSIVE, PRESSURE SENSITIVE CRYSTALS UNDER THE CAP.

  
Tom Pullizzi
Falls Township, Pennsylvania