Exercise 13. Antimony Sulfate

Like ferric nitrate, antimony sulfate is decomposed by water, various basic salts being formed, the simplest of which has the formula (SbOLSCL. The normal salt is stable only in rather concentrated sulfuric acid. Since this latter solvent has almost no vapor pressure at ordinary temperatures, the moist salt cannot be dried by evaporation of the solvent. It cannot be dried on absorbent paper, since the oily liquid rapidly carbonizes it. In such a case, it is best to take advantage of the drying qualities of unglazed earthenware (porous plate), such as the biscuit which forms the body of dishes. Owing to the fine pores which this material contains, liquids are sucked up by it by capillary attraction, and it is not acted upon by most reagents. 

Powder very finely 20 g. of antimony oxide, Sb2C 3 (or metallic antimony), and add this in small portions at a time to 250 cc. of hot concentrated sulfuric acid contained in an evaporating dish. Maintain the heat until all of the powder has been dissolved, if necessary adding a little more acid to keep the white sulfate in solution. Allow the solution to cool and filter off the fine crystals on a platinum cone or a Witte plate with very small holes, pumping them as dry as possible. Spread the pasty mass on pieces of unglazed dishes, putting one such piece on top of another, to make a pile that consists of alternate layers of plate and sulfate. Put the entire pile in a desiccator so as to prevent absorption of moisture from the air. If the sulfate is rather wet, it may be necessary to scrape it off the plates and repeat the operation with fresh ones. Finally, spread 

Additional Exercises Mercurous sulfate, Hg2SO.i, Baskerville and Miller, J. Am. Chem. Soc., 19, 873 (1897) Bismuth sulfate, Bi2(SO )3, Allen, Am. Chem. J., 27, 284 (1902). 

The method of preparing salts by double decomposition can be employed in so many cases that it is important to understand thoroughly the principles involved in the procedure and to acquire skill in the necessary manipulation. 

In general, when two salts are brought together in solution, a new simple salt, resulting from double decomposition, may crystallize from the solution or a double salt, a complex salt, or a solid solution may be formed. The first case only will be considered at this time, others being deferred to later exercises. 

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