How to measure the volume of gas produced?

July 16, 2008 6:48 AM

I would like to find out how much gas I can produce by electrolysis using homemade stuff. Is there any cost efficient/accurate way to measure the quantity of gas produced?

I was thinking of simply using a balloon but I believe that it won't be that accurate.

Basically what I have is a closed system (a small reservoir) which will produce gas. I would like to quantify gas production quite accuratly in order to do some analysis of what can be done with it.

posted by pigelb to science & nature (6 comments total)

Loss of mass in the reservoir, then estimate gas generation through stoichiometry?
posted by scruss at 7:32 AM on July 16, 2008

Well from when I've watched some of the 'water 4 gas' videos or HHO generation videos, what I've often seen used is simply cutting the bottom off of an empty 1-liter soda or water bottle, filling with and then submerging it in water, the have a hose going from the chamber generating the gas up to and under the bottom of the bottle (which is currently filled with water). Then it's just a matter of timing how long it takes for the gas to fill up the water bottle and you know that you are producing X Liters of gas every Y minute(s).
posted by MarkLark at 7:38 AM on July 16, 2008 [1 favorite]

Why not use the Archimedes method? Dunk the balloon in a beaker and see how much the volume changes.
posted by greatgefilte at 8:33 AM on July 16, 2008

Allow the gas to displace a certain amount of water in an inverted, graduated, buret.
posted by mahoganyslide at 8:56 AM on July 16, 2008

Use warm water so that the gas has a low solubility. I would say ideally something around 90 C, and do your electrolysis in an upside down water-filled graduated cylinder. Use inert electrodes, so that you don't lose oxygen to making rust.

You should expect to get a couple ml of gas for every ten amp-seconds of electricity. Adjust the graduated cylinder so that the water level is level with the gas level inside when you do your measurements, to ensure that it is at atmospheric pressure. Also remember your gas is warm because your water was warm.
posted by aubilenon at 11:56 AM on July 16, 2008 [1 favorite]

As long as you don't need continuous flow, take a rigid container of known volume and mount a pressure gauge to the valve, then calculate back from PV=nRT. Keep in mind that if pressure gets high enough the gas won't be well approximated as an ideal gas anymore and you should use the van der Waals corrections. (Wikipedia: http://en.wikipedia.org/wiki/Van_der_Waals_equation).

By the way, I'm guessing that ``hydrolysis'' means you're making oxygen and hydrogen. You're keeping those in separate containers, right?
posted by d. z. wang at 12:01 PM on July 16, 2008