SODIUM PERBORATE 211
dry keeps fairly well, but if it is left suspended in the solution it
gradually loses oxygen and the sodium metaborate goes back into
solution:
Materials: borax, Na 2 B 4 O 7 -10H 2 O, 24 grams = 0.0625 F.W.
NaOH, 5 grams.
3 per cent H 2 O 2 solution, 283 cc.
alcohol,
ether.
Apparatus: 600-cc. beaker.
suction filter and trap bottle,
pan of ice.
iron ring and ring stand.
Bunsen burner.
Procedure: Dissolve the 24 grams of borax and 5 grams of
NaOH in 150 cc. of warm water. Cool the solution to room
temperature and add the 283 cc. of hydrogen peroxide slowly.
Cool the solution by immersing the beaker in ice water, finally
dropping 20 grams of ice into the solution. Stir; after a few
minutes fine crystals begin to separate. Stir frequently for the
next 20 minutes. Then collect the crystals on a suction filter.
Wash the crystals with two successive portions of 25 cc. each of
alcohol and then two successive portions of 25 cc. each of ether.
Stop the suction before each washing and let the washing liquid
sink into the crystals before applying suction again. Dry the
crystals on paper towels and preserve them in a 2-ounce cork-
stoppered bottle.
QUESTIONS
- To 50 cc. of water, add 1 cc. of KI solution and 1 cc. of starch
emulsion. Note absence of blue color. To half of this starch-
iodide solution, add a few crystals of sodium perborate and then a
drop or two of acetic acid until a blue color appears. To the other
half of the starch-iodide, add a few drops of hydrogen peroxide
and note a blue color which disappears when a drop or two of 6 N
NaOH is added. Write equations and compare the action of
sodium perborate and hydrogen peroxide.
- To 50 cc. of water, add 1 gram of sodium perborate and 10 cc.
of QN H 2 SO 4. Dissolve 0.1 gram of potassium permanganate in
10 cc. of water and add 5 cc. of 6N H 2 SO4. Pour this solution
