How to Determine Normality of Sodium Thiosulfate

Principle

Potassium Dichromate reacts with Potassium iodide in acidic medium to liberate iodine (I₂). The liberate iodine (I₂) then titrate again Sodium thiosulfate (Na₂S₂O₃) Solution.

Appratous Requirement

• Volumetric flask
• Burette
• Pipette
• Conical flask (Erlenmeyer flask)
• Beaker
• Measuring cylinder
• Stirring rod
• Funnel
• Dropper
• White tile (for better visibility during titration)
• Wash bottle (for distilled water)

Procedure of Sodium Thiosulfate

• 10 ml K₂Cr₂O₇
• 25 ml water.
• 5 ml conc. HCl
• KI 10% 20 ml.
• 5 minutes shake in dark Room place 20 minutes.
• 75 ml to 100 ml D.W.
• Titrate with 0.1 N Na₂S₂O₃
• Shaking continuously untill yellow colour.
• using starch indicator (3 ml).
• Titrate until green colour appears from black.

Calculation

V1N1=V2N2

N1=V2N2/V1

Result

The Normality of Sodium thiosulfate (Na₂S₂O₃) solution is calculated using the formula and Normality (N)