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Posted by Sourabh Singh 6 years, 11 months ago
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Yogita Ingle 6 years, 11 months ago
The preparation of potassium dichromate from chromite involves the following main steps:
(i) The chromate ore is finely ground and heated strongly with molten alkali in the presence of air.
2FeCr2O7 + 8NaOH + 7/2 O2 → 4Na2Cr2O7 + Fe2O3 + 4H2O
(ii) The solution of sodium chromate is filtered and acidified with dilute sulphuric acid so that sodium dichromate is obtained.
2FeCr2O7 + H3SO4 → Na2Cr2O7 + Na2SO4 + H2O
(iii) A calculated quantity of potassium chloride is added to a hot concentrated solution of sodium dichromate. Potassium dichromate is less soluble therefore it crystallizes out first.
Na2Cr2O7 + 2HCl → K2Cr2O7 + 2NaCl
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