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

104 PEROXIDES.

peratures, offers an excellent opportunity for studying the effect of various

catalyzers. In this way a remarkable analogy between organic ferments and

inorganic catalyzers has been discovered. Cf. No. 20. Hot solutions of hydro-

gen peroxide are decomposed rapidly at the rough places on porcelain or glass

apparatus.

A. Hydrogen Peroxide from the Oxy-hydrogen Flame. Let a

hydrogen flame one-half centimeter long, burning from a glass

tip, play against a piece of ice in a watch glass, until all the ice

is melted. The presence of hydrogen peroxide in the resulting

liquid may be easily shown by means of a titanium solution

(see p. 83).

B. Hydrogen Peroxide from Barium Peroxide. Add, little by

little, some pulverized, crude barium peroxide' (No. 66) to a

mixture of 0.6 of its weight of concentrated sulphuric acid and

300 c.c. of water; the liquid must be kept cold by ice both
inside and outside the vessel. Neutralize the excess of acid with

barium carbonate, let the precipitate settle, filter, and distil the

solution on the water bath.

For the distillation use a liter round-bottomed flask with a
stopper through which pass two glass tubes; one is quite narrow
and terminates below in a long, fine capillary and above in a
rubber tube with a screw-cock. The other tube leads from the
flask to a long condenser; the lower end of the latter is fitted to
a suction bottle which serves as a receiver. All parts of the
apparatus must be closed with tightly-fitting stoppers. Evacuate

the apparatus, but allow a fine stream of air bubbles to flow con-

tinuously from the capillary through the liquid in the flask, in

order to avoid bumping; the rate of flow of this air current is to
be regulated by the screw-cock. Distil over about one-third of

the contents of the flask and test the distillate for hydrogen per-

oxide as described below; it should be practically pure water.

Then empty the receiving bottle and distil as before until all of
the remaining liquid has passed over.

Qualitative Tests for Hydrogen Peroxide.

1. Titanium Sulphate Test (cf. p. 83).


2. Chromic Acid Test: To a few c.c. of a chromate solution

weakly acidified with sulphuric acid, add a few drops of hydrogen

(^1) The use of barium peroxide hydrate has also been recommended.