Karl Fischer water determination template

Volumetric Karl Fischer titrator: reagent bottle, dosing burette, sealed stirred cell with a double platinum electrode, sample injected by syringe through a septum. University analytical.

What the template shows

• Measure the water in a sample by its reaction with iodine and SO₂
• I₂, SO₂ and a base (imidazole) in methanol: H₂O + I₂ + SO₂ + CH₃OH + 3 RN → [RNH]SO₄CH₃ + 2 [RNH]I
• Dosing burette
• Water = volume added × titre (mg H₂O per mL, set with pure water)
• For ppm water use the coulometric type, which makes I₂ at an anode
• Sample by syringe
• Through the septum, tip under the methanol; weigh the syringe before and after (by difference, to 0.1 mg)
• Drying tube
• Molecular sieves keep room moisture out
• Double Pt electrode
• Polarised: current flows once free I₂ is in excess (end point)
• Titration cell
• Dry methanol, stirred and pre-titrated to dryness before the sample goes in
• Reaction setup

Drawn with 11 shapes – every one editable in MolDraw.

Sources

• Furniss et al., Vogel's Textbook of Practical Organic Chemistry, 5th ed., Longman 1989 Textbook