70 WATER AND SOLUTION
Drop some aluminum turnings into some sodium hydroxide
solution. Note that gas is immediately given off and that the
aluminum in time dissolves completely. The gas is found to
burn like hydrogen.Insoluble aluminum hydroxide is known to react readily with
sodium hydroxide producing the soluble sodium aluminate
A1(OH) 3 + 3NaOH -> Na 3 A10 3 + 3H 2 OWith the aluminum hydroxide coating thus continually removed
by the sodium hydroxide there is nothing to prevent the progress of
the primary reaction between aluminum and water.
2A1 + 6H 2 O -» 2A1(OH) 3 + 3H 2- Chlorine and Water. The " chlorine water" in the re-
agent bottle is prepared by dissolving chlorine gas in water.
Take a few cubic centimeters of this solution and (to make
sure that it has been acted upon by light) expose it a few min-
utes to direct sunlight or for a longer time to strong diffused
daylight. Boil the solution under the hood to drive off any
chlorine which is left, and then test the liquid with litmus.
The litmus is turned red. Fill a test tube with chlorine water
and invert it in a small beaker containing chlorine water.
Leave the whole in the bright sunlight for several hours. A
few cubic centimeters of a colorless gas collect in the top of the
inverted test tube, and the yellow color of the chlorine water
gradually fades out. The gas causes a glowing splinter to
burst into flame, which identifies it as oxygen.
Metals more active than hydrogen displaced that element from
water. Non-metals, on the other hand, if active enough, would
displace the oxygen. It is obvious that this is what has happened
and that the acid remaining in solution is hydrochloric acid, HC1.
The total effect of the change is given by the equation
2C1 2 + 2H 2 O -> 4HC1 + O 2
That chlorine is not greatly more active than oxygen is shown by
the fact that this reaction does not take place in the dark, and only
slowly under the action of sunlight.