Studies of Potassium Trisoxalato Cobaltate III

This compound is easily prepared by oxidation of cobalt(II) carbonate, with lead dioxide in presence of oxalic acid and potassium oxalate. It can be analysed for oxalate by permanganate titration and for cobalt by titrating iodine liberated on adding K1 to the acidified solution, after precipitating cobalt(III) oxide. 

Allow to crystallise and then filter the product under suction. Wash twice with a little alcohol and dry by continued suction while pressing between filter paper. Weigh the product to the nearest eg and calculate the percentage yield. Store in the dark in a fridge. 

Transfer the filter paper carefully and quantitatively to a conical flask acidify liberally with dilute HCl after adding 1.5 g Kl. Cover with a watch glass and allow to stand until all the black C02O3 dissolves. Titrate the liberated iodine against standardised 0.05 M thiosulphate, adding 2 cm freshly prepared starch solution when the colour is straw yellow. Calculate the % Co in your preparation and hence its % purity. 

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