250 OXY-ACIDS AND SALTS OF THE NON-METALS
there the conditions were such that a salt of iodic acid was obtained
rather than the free acid or its anhydride. Starting with this salt,
however, the free acid is obtained by metathetical reactions which
depend on the insolubility of barium iodate and the still greater
insolubility of barium sulphate.
Materials: potassium iodate, KIO 3 , 43 grams = 0.2 F.W.
barium nitrate, Ba(NO 3 ) 2 ,26 grams = 0.1 F.W.
362VH 2 SO 4 , 8cc.
162V HN0 3
Apparatus: 600-cc. beaker.
750-cc. casserole,
suction filter and trap bottle,
iron ring and ring stand.
Bunsen burner.
Procedure: Dissolve the potassium iodate and the barium ni-
trate, separately, each in 250 cc. of hot water, and mix the two
solutions at the boiling temperature while stirring well. Cool the
mixture, let the heavy precipitate settle, decant off the clear liquid,
and wash the salt twice by decantation with pure water. Drain
the barium iodate on a suction filter, and wash it on the filter with
cold water. Then remove it to a porcelain casserole, suspend it in
250 cc. of water, heat to boiling, and stir in a solution of 8 cc.
36 2V H2SO4 in 100 cc. of water. Keep this mixture well stirred at
the boiling temperature for at least 10 minutes, since the conver-
sion of solid barium iodate into solid barium sulphate is a reaction
that requires some time. Filter the solution and rinse the last
of the iodic acid from the solid barium sulphate by washing two
or three times on the filter with small portions of water. Evapo-
rate the solution in a casserole to a small volume, and finally,
holding the casserole in the hand, keep the contents rotating, so
that the whole inside of the dish is continually wet. Continue
evaporating until solid iodic acid separates in some quantity.
Cool completely and rinse the crystals with three successive por-
tions of 10 cc. each of 162V nitric acid, triturating the crystals
thoroughly with each portion of the acid. Warm the casserole
carefully until the product is perfectly dry and ceases to give off
acid vapors. This warming will convert the iodic acid to a large
extent into the anhydride I2O5. Place the iodine pentoxide at
once in a 2-ounce cork-stoppered bottle.