Testing Method of Fe Element in Sodium Tungstate 2/2

Another method for testing Fe element in sodium tungstate:
1.Be ready with:
(1)Ferric trichloride solution(FeCl3)
(2)Indicator : sodium diphenylamine sulfonate
(3)Potassium bichromate titrant
(4)250ml dried beaker flask
(5) Funnel inserted with filter paper and small piece of cotton(used for filtration in the later process)
2.Add 1.0g sodium tungstate sample into beaker flask, and then add 50ml FeCl3 solution, jam-pack with rubber plug, shake it fiercely for 15 minutes.
3.Suck-filter the solution from step 2 by suction flask with funnel( inserted with filter paper and small piece of cotton). The filtrate is obtained.
4.Clean the beaker flask for 4-5 times and filter the residue.
5.Adding 15ml mixed acid of sulphoric acid and phosphoric acid, and then adding water to dilute it until 100ml.
6.Adding five drops of 5g/L sodium diphenylamine sulfonate, titrate by potassium bichromate titrant until it turns into bluish violet.
7.Fe content is calculated by : Fe⁰(%)=Vf_Fe0/m x 100
Among which:  f_Fe0 —— quantity of metal ferric calculated by gram which equals to 1ml potassium bichromate titrant.
V——volume of consumed potassium bichromate titrant during titration.
m——quantity of sodium tungstate sample.

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