The Hoffman Voltameter: Mark II

Following on from my first attempt, I’ve built a new version:

Hoffman Voltameter Mark II (it's a bit better)

This version has smaller bottles, reducing the amount of electrolyte needed, and goes back to using silicone sealant to attach the PEX piping to the bottles.

The glue gun was just too leak prone. Although it was much quicker to work with, the glue is very rigid when dry, so handling the apparatus (eg when filling or emptying) tended to create leaks. So I decided to be patient, and use sealant, which is much more flexible when dry. I also sanded the area around the holes in the bottles, and the ends of the PEX pipes, so that the sealant would adhere more effectively.

This version works much better! It’s leak-free, and I succeeded in generating about 100ml of hydrogen and collecting it by releasing the clamp and using a makeshift gas bubbler. I passed it over a flame, and heard the squeaky pop — perhaps the best one I’ve *ever* heard, considering the effort it took!

Unfortunately, I had a little less luck with the Chlorine. A small quantity of gas was generated at the anode, but I could not discern any particular colour. Conversely, the electrolyte in the anode bottle had a definite green tinge. I suspect that the Chlorine is largely dissolving in the water, and that the gas I collected at the top was probably a small amount of Oxygen. This feels more plausible than it otherwise would given that the electrolyte was not a saturated solution. I’ll test this out later.

However, this version isn’t without its problems. There’s some visible corrosion around the join between the electrode and the wire, which I tried to insulate using heat shrink. As it’s clear that the steel connection is being oxidised, that’s obviously not working. I also don’t like that the electrodes are dangling from cables. It feels… bad. So, I’m going to take the plunge and mount them permanently to the bottles from the outside, which will remove the steel connection from the electrolyte entirely as well as making it all a bit neater.

Another very strange problem is that the water level in the three containers is not always the same, even when the tubes are open to the atmosphere. This is a bit baffling, to say the least. I think that the tubes are probably at fault: their internal diameter is very small (about 2mm) and I think there’s some kind of capillary effect at work. I’m going to replace these with some normal 5mm PVC tubing and see if that solves the problem.

This version is much better than its predecessor, and I’ve experienced some success. But I think there’s better to come.