Laboratory Methods of Inorganic Chemistry, 2nd English Ed. 1928

POTASSIUM BROMATE. 121

nearly accomplished, add 1 g. more of iodine. Concentrate by
evaporation until on cooling nearly all of the potassium iodate

crystallizes; collect the product on a filter, and recover what is left

in the mother-liquor by evaporation.

Dissolve the crude product, which always contains some acid

salt, in 150 c.c. of hot water, and neutralize exactly with potassium

hydroxide. On cooling a good yield of the pure salt is obtained.

Ignite a little of the product in a porcelain crucible, and test the

residue for chloride by distilling it with potassium bichromate and

concentrated sulphuric acid, and passing the vapors into ammonia

water.

78. Potassium Bromate and Potassium Bromide.
    To a solution of 62 g. potassium hydroxide in 62 g. of water,
    add 80 g. of bromine drop by drop while cooling by means of tap
    water. (Hood.) The solution soon becomes colored a permanent
    yellow, and later a crystalline powder of potassium bromate sepa-
    rates; after cooling completely, collect the bromate on a filter and
    purify it by recrystallization from 130 c.c. of boiling water. Com-
    bine all the mother-liquors and evaporate them to a semi-solid
    mass; mix this thoroughly with 5 g. of powdered wood-charcoal,
    dry it completely and then heat it to redness for an hour in a large
    porcelain crucible surrounded by an asbestos or sheet-iron funnel.
    Treat the sintered mass with 120 c.c. of hot water, and then

wash the residue with 20 c.c. more of water; evaporate the filtered

solution to crystallization. The yield is 26 to 27 g. of KBrO 3 and

90 to 95 g. of KBr.

The addition of acid to the aqueous solution of either one of

these salts should not produce a yellow coloration, due to the

separation of free bromine.

(c) Nitrites and Nitrates.

79. Sodium Nitrite from Sodium Nitrate.
    Sodium nitrate, when melted with a reducing agent such as lead, loses
    one-third of its oxygen and goes over into the nitrite.
    In the absence of reducing agents sodium nitrate can be melted without
    decomposition; at higher temperatures, however, a dissociation, although
    incomplete, takes place according to the equation:
    NaNO 3 = NaNO 2 + O.
    From the above facts the conclusion may be drawn that this dissociation of
    sodium nitrate takes place even at more moderate temperatures, although
    to so small extent that it can be proved only indirectly. The reducing agent