Synthetic Inorganic Chemistry

POTASSIUM PERCHLORATE 251

To obtain completely anhydrous iodine pentoxide, the product

could be heated for some time in an oven at about 200°. Crys-

tallized iodic acid could be obtained by dissolving the product

in a very little water, in which it is extremely soluble, and allowing

the solution to evaporate slowly.

QUESTIONS

1. Dissolve a little of the iodine pentoxide in water. Test the
   solution to show whether it contains a strong acid. How?


2. Heat 0.5 gram of iodine pentoxide in a dry test tube. Insert
   a glowing splinter in the tube. Note whether the entire substance
   can be volatilized; also if any of the original substance deposits in
   the cooler part of the tube.

PREPARATION 39
POTASSIUM PERCHLORATE, KCIO4
When potassium chlorate is heated to about 400° it may de-
compose according to either of the following independent reactions:
4KC1O 3 = KC1 + 3KC1O 4 (1)
KCIO3 = KC1 + liO 2 (2)
The second reaction is accelerated by catalyzers, such as man-
ganese dioxide or ferric oxide, or in fact any material with a rough
surface. Too high a temperature also causes reaction (2) princi-
pally to take place. On the other hand, if the temperature is
maintained at the right point, the salt is free from dirt, and the
inside of the crucible is perfectly clean and free from roughness,
the decomposition proceeds mainly according to reaction (1).
Potassium perchlorate is very sparingly soluble in cold water and
may be separated from potassium chloride and any undecomposed
potassium chlorate by crystallization.

Material: potassium chlorate, KC1O 3 , 61 grams = 0.5 F.W.

Apparatus: 100-cc. porcelain crucible and cover,

suction filter and trap bottle,

iron ring and ring stand.

Bunsen burner.

Procedure: Place 61 grams of potassium chlorate in a dry, clean

100-cc. porcelain crucible, the glaze of which is in perfect condition.