how to prepare crystal of potash alum in home ?
Answers
(i) Take about 3 g of potassium sulphate crystals in a 250 ml beaker. Add about 25 ml of distilled water. Stir with a glass rod to dissolve the salt. Heat if necessary.
(ii) Take about 12 g of aluminium sulphate crystals in another beaker. Add about 25 ml of distilled water and a few drops of dil. sulphuric acid (to prevent the hydrolysis of aluminium sulphate). Stir with a glass rod to dissolve the salt. Heat if necesary. Filter if the solution is not clear.
(iii) Mix the two solutions by transferring them into a china dish. Heat the china dish gently on a water bath to concentrate the solution up to the crystallization point.
(iv) Allow the solution in the china dish to cool undistrubed by placing it over the mouth of a beaker filled with cold water for some time. White octahedral crystals of potash alum are obtained.
(v) Separate the crystals by decanting off the mother liquor.
(vi) Wash the crystals with a small amount of ice cold water.
(vii) Finally dry the crystals either by placing them between folds of filter paper.