BARIUM PEROXIDE 139have a suspension of the copper oxide from which all air has been
expelled. Add a few drops of 6iV HC1 and observe very closely
for "effervescence," that is, for bubbles of escaping gas. Such
gas would be carbon dioxide and would show that the copper car-
bonate had not been entirely decomposed. When the test shows
the absence of carbonate, transfer the solid to a 2-ounce cork-
stoppered bottle.
QUESTIONS- Could hydrochloric acid take the place of nitric acid in this
preparation? Explain. - Basic copper carbonate is a variable mixture of copper car-
bonate and copper hydroxide. Assuming that it has the composi-
tion Cu(OH)2-CuCO 3 , write intersecting ionic equations to show
how it is formed. What type of ionic reaction does this illustrate?
PREPABATION 6
HYDROGEN PEROXIDE AND BARIUM PEROXIDE HYDRATE,
HA AND BaO 2 -8H 2 O
The ordinary oxide of barium has the formula BaO, and it forms
the corresponding base Ba(OH) 2 when it combines with water.
Barium salts are formed when this base is neutralized with acids.
In addition there is another oxide of barium containing twice as
much oxygen, BaO 2 , which is easily obtained when barium oxide
is heated to a dull red heat in air free from carbon dioxide.
This oxide, however, does not behave like an ordinary oxide;
for example, it does not react with water to give such a base as
Ba(OH) 4 nor with acids to yield such a salt as Ba(NO 3 ) 4. Both
oxygen atoms seem to be present as a single radical having the
same valence, namely 2, as the simple oxygen radical in ordinary
barium oxide, because, when barium peroxide is treated with acids,
the ordinary barium salt and hydrogen peroxide are formed.
BaO 2 + 2HC1 -» BaCl 2 + H 2 O 2The name peroxide has been given to oxides which contain the
O 2 ~ ~~ radical and which yield hydrogen peroxide when acidified with
acids.
The common heavy metals do not form peroxides; only the
most strongly metallic elements such as the alkali and alkaline
earth metals do so. For example, when sodium metal burns freely