Collecting Hydrogen and Oxygen: In this instructable I'll give you a simple way to collect Hydrogen gas and if you want also, to collect Oxygen. Depending on the voltage and current that you use for the project this could be hazardous. 4 volt power drill battery pack f.
Oxygen has much the same density as air, and you can collect it like this if you want it to be dry. Otherwise you would choose to collect it over water. You can collect any gas this way, and would use it if you wanted to measure its volume.
You can use it for hydrogen and ammonia. You can't use this for the light gases, but heavier ones like carbon dioxide and chlorine can be collected in this way. Oxygen has much the same density as air, and you can collect it like this if you want it to be dry. Otherwise you would choose to collect it over water.
Do not mix the hydrogen and oxygen in this way unless you have a properly protected explosion proof setup, as Brown's gas is explosive. Hofmann Apparatus - Split Water 2H2+O2: Hofmann Apparatus - Split Water into Hydrogen and Oxygen My fascination with the electrolysis of water into hydrogen and oxygen gas started at a young age.
Can a gas tube be used to collect hydrogen & oxygen?
There is no problem collecting hydrogen and oxygen like this. This only works if the gas is lighter than air. A heavier gas would simply fall out of the tube. You can use it for hydrogen and ammonia. You can't use this for the light gases, but heavier ones like carbon dioxide and chlorine can be collected in this way.
Along with making hydrogen and oxygen, you can also create oxide salts, such as metal+Oxygen (i.e., Fe2O3), although this will not allow you to collect gaseous oxygen. Instead, you can make pigments out of these, such as turquoise blue with Copper or orange with Iron.
This page looks at how you can collect and test samples of hydrogen, oxygen, carbon dioxide, ammonia and chlorine in the lab. It looks at four simple ways of collecting gases - over water, downward into a test tube or gas jar, upwards into a test tube or gas jar, and into a gas syringe.