OXIDES AND WATER 73deflagrating spoon made by winding a piece of wire around a
piece of chalk one end of which has been scooped out. A
large piece of charcoal should be attached to a wire and held
in the flame until it glows brightly before it is put in the jar.
Quickly add 3 to 5 cc. of water to each bottle, close it with a
glass plate (or the palm of the hand), and shake vigorously a
few moments. Test the solutions with litmus. In each case
the litmus turns red.This experiment shows that non-metals form oxides which react
with water to
4Pc-+ 5O 2- 0 2 -^
hO 2 -
produce acids.
-> 2P 2 O 5- so 2
co 2
P 2 O 5 -
SO 24
co 2 -f 3H 2 O -* 2H3PO4- H 2 O ^± H 2 SO 3
h H 2 O ^ H 2 CO 3
The oxides of phosphorus and sulphur are quite readily soluble
but carbon dioxide is very much less soluble.
WATER CONTAINS TWO SEPARATELY REPLACEABLE PORTIONS
OF HYDROGEN
When sodium or calcium reacts with water hydrogen is liberated
and sodium or calcium hydroxide is formed. The formula
NaOH or Ca(OH) 2 shows that the compound still contains one-half
of the hydrogen of the original water, but let us imagine for a
moment that we are in the place of the early chemists who were
rinding out things for the first time. They carefully dried these
hydroxides and then tried experiments to see if any more hydrogen
was obtained from the hydroxides. When they found that they
could obtain an amount of hydrogen just equal to that displaced
from the water by the metal when the hydroxide was prepared,
they drew the conclusion that water contained two parts of hydro-
gen in combination with one part of oxygen. This experiment was
one of the strong arguments which led to the adoption of the
formula H 2 O for water rather than HO.
- Mix 2 grams of dry powdered sodium hydroxide and
3 grams of zinc dust in a mortar. Place the mixture in
a hard glass test tube fitted with a delivery tube. Heat the
mixture in the tube; collect a little of the evolved gas and
show by a test that it is hydrogen.