160 NON-METALLIC ELEMENTS IN BINARY COMPOUNDStions according to the powers of 10 until a solution is obtained
which shows a distinct yellow color with the titanium sulphate,
while the next dilution fails to show the test. In the final tests
add 1 cc. of reagent to 15 cc. of pure water and hold this beside
the sample being tested, looking through the length of the
column of liquid and placing a piece of white paper for a back-
ground. By comparing with a " blank " (the pure water plus
reagent) in this way the fainter colors may be recognized with
much more certainty. Express the sensitiveness of the test
as the number of parts of water in which 1 part by weight of
hydrogen peroxide can be diluted and still give a distinct test.
This test is characteristic for hydrogen peroxide and can be
used to differentiate peroxides from simple oxides and dioxides.We are now going to investigate the behavior of a number of
oxides with acids and we are going to use the titanium sulphate
reagent to discover whether or not hydrogen peroxide is formed
by the action.
- Peroxides, (a) To 1 gram of barium peroxide, BaO 2 ,
in a small beaker add 15 cc. of water and then 6iV HN0 3
drop by drop with continuous stirring until the solid has
dissolved. Test the solution for hydrogen peroxide by
adding titanium sulphate. In order to convince yourself
whether or not the effect could have been caused by the nitric
acid, treat 1 gram BaO 2 with 5 cc. of water and 5 cc. 6iV
H2SO4. Here a clear solution cannot be obtained because
insoluble barium sulphate forms. Filter off the insoluble
residue and test the filtrate with titanium sulphate. The
same yellow color is obtained as before.
(6) Test barium oxide BaO in the same way. Since this
oxide reacts vigorously with water to form the hydroxide,
Ba(0H) 2 , we might as well use the hydroxide as a starting
point, but should bear in mind that it is essentially the same
thing as the oxide BaO. No yellow color appears when
titanium sulphate is added.
(c) Heat a porcelain crucible cover on a triangle to red-
ness; drop upon it a piece of sodium metal the size of a small
pea, and remove the flame. The sodium burns to form sodium
peroxide Na 2 O 2. Place 50 cc. of cold water and 5 cc. of
6 N H 2 SO 4 in a small dish; let the porcelain and adhering