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Testing the strength of your metabisulphite or SO₂ stock solution

1 - To test the strength of your powdered Na₂S₂O₅₂ or K₂S₂O₅₂ (sodium or potassium bisulphite), make up a standard stock solution.

2. - To test the strength of your SO₂ stock solution, pipette 1 ml of stock solution to 1 L of water and mix gently. This is the equivalent of 100 ppm SO₂

Since there are no SO₂ binding compounds present in water, all the SO₂ will exist as free SO₂ (FSO₂ ).

3. - Determine the FSO₂ (free SO₂) by the aspiration/oxidation method.




				.…..	ppm (FSO2 determined)
Percentage strength of stock solution		=		------------	-----------------------------	------------		X		100 %
					100 ppm