EXPERIMENTS 257The hypochlorite solution contains OCF ions, and the fact that
this solution does not bleach rapidly indicates that the ions are not
the principal bleaching agent. Addition of sulphuric acid pro-
duces un-ionized hypochlorous acid, H+ + OC1~ —• H0C1, the
ionization of this acid in 0.1 N solution being 0.06 per cent. Thus
it is clear that HOC1 must be the principal bleaching agent.
That the hypochlorite solution did bleach the cloth slowly might
have been due to a slow action of the OC1~ ion, or perhaps to a
small amount of HOC1 produced by hydrolysis of the salt, or set
free by the action of carbonic acid from the air. That no bleaching
occurs after adding the NaOH settles this point, because no free
H0C1 can remain in presence of the base.
This experiment shows that the salt of hypochlorous acid is
more stable than the acid itself.- Hypobromites. Add a few drops of bromine to 2 cc.
of 6N NaOH diluted with 5 cc. of water. The red color of
the bromine disappears. Dip colored cloth and litmus paper
in this solution and then in dilute H2SO4, to show that it
bleaches in the same way as a hypochlorite solution.
Add a part of the solution to 2 cc. of NH4OH and notice
that there is effervescence, the escaping gas being non-com-
bustible and a non-supporter of combustion (nitrogen). (See
Preparation 19.)
Add the rest of the solution to a solution of 0.25 gram of
urea in 5 cc. of water and notice a similar effervescence.
Hypobromites are very similar in properties to hypochlorites
and oxidize organic coloring substances. Ammonia and urea are
oxidized, even in alkaline solution, by hypobromite,
3NaOBr + 2NH 3 -»3NaBr + 3H 2 O + N 2
3NaOBr + CO(NH 2 ) 2 -»• 3NaBr + CO 2 + 2H 2 O + N 2- Chlorates and Bromates. The formation of chlorate
and bromate by heating hypochlorite and hypobromite, re-
spectively, is illustrated in Preparations 35 and 36. Test-
tube experiments may be tried, adding excess of chlorine and
bromine respectively to hot 6N KOH, boiling a little and
cooling, whereupon the sparingly soluble potassium chlorate
and potassium bromate crystallize out.