The term gas can not be used to identify a mixture that has the same composition throughout. Gas is a state of matter.
One way to test a gas to identify it as an HCL gas is to dip a glass rod in ammonia and place it in the gas. If a white smoke is produced, the gas is HCL gas.
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Condensation
ball juice
How do you identify what gas is in a compressed gas cylinder
It is a mustard yellow and kills people
respirometer
This depends on the gas and concentration; many tests exist based on the reaction of gas with a specific reagent.
Light a wooden splint and dip it in the gas. If it is Carbon Dioxide, it will put the fire on the end out.
precipation. from the clouds
oil and gas