gcsescience.com                            Tests for Other Gases                            gcsescience.com
Testing for Gases.

There are general tests for gases.
Some gases have a specific test.

General tests.

1)  Has it a colour?

2)  Has it a smell?
All gases which smell are poisonous
(but not all poisonous gases smell, eg. carbon monoxide).

3)  Does it change the colour of moist litmus paper
or moist universal indicator paper?

Some gases are acid or alkaline in water.
Using moist paper allows a little of the gas to dissolve in the water,
to form acid ions (H⁺), or alkaline ions (OH^-).

Acid ions will turn blue litmus paper red,
or universal indicator paper orange to red.

Alkaline ions will turn red litmus paper blue,
or universal indicator paper blue to purple.

4)  Does it burn, or support burning?
Note that these two are not the same.
Some gases will burn. Only oxygen will support burning.
Test with a lit splint.

Specific test.

Some gases have a test which only that gas will perform.
The test is specific for the particular gas concerned.
It is the specific test which is the one to remember,
since it positively identifies the gas.

gcsescience.com     Contents     The Periodic Table     Index     Quizzes    gcsescience.com

Copyright © 2008 Dr. Colin France. All Rights Reserved.