http://en.wikipedia.org/wiki/Hofmann_voltameter
As I interpret the above reference, a Hoffman apparatus requires platinum electrodes if it is to generate hydrogen. Otherwise metal from one electrode will plate on the other.
Are you using platinum electrodes?
Hi,
i recently constructed a hofmann apparatus at home out of pvc and had some trouble with it. Basically, once it is set up, i only get gas from one electrode, the other does nothing. H2SO4 is used as the electrolyte, and the is 12 volts at 4 amps being put through it, DC. are there any simple flaws i am over looking as i just want to keep the oxygen and hydrogen separate.
thanks, your help is greatly appreciated.
9 answers
no, both electrodes are made of copper and the electrodes shouldn't matter, as long as they conduct
I stand by my previous answer. See
http://www.qsinano.com/news/releases/2006_06_08.php
There are acceptable substitutes for platinum in H2O electrolysis to produce H2, but copper is not one of them.
http://www.qsinano.com/news/releases/2006_06_08.php
There are acceptable substitutes for platinum in H2O electrolysis to produce H2, but copper is not one of them.
You can successfully use mechanical pencil leads as electrodes in a demonstration apparatus, but the clay/carbon "lead" is not a good conductor and the amount of gas produced is not high.
would you be able to explain why for me?
why can't copper be used? why does this result in none of one the gases being given off?
The metal composition of the electrodes doesn't matter as far as generating H2 and O2 gases initially. However, it is desirable for the composition of the two electrodes to remain constant so that their performance will not change during electrolysis. Platinum works very well but it is expensive.
If the water is made conductive by adding a little sulfuric acid, H2SO4, lead electrodes (yes, LEAD) would work well for a while. An even better cheap choice is lead solder wire. A copper anode would dissolve gradually forming a copper salt in solution.
If the water is made conductive by adding a little sulfuric acid, H2SO4, lead electrodes (yes, LEAD) would work well for a while. An even better cheap choice is lead solder wire. A copper anode would dissolve gradually forming a copper salt in solution.
Just to add my 2 cent's worth:
You also could use graphite or carbon rods such as those from old worn out flashlight cells, specifically such as those that come from D or C cells. The why it won't work, at the anode, it is easier for Cu to go into solution (Cu ==> Cu+2 + 2e for which Eo = -.34 volts than it is to oxidize water
2H2O ==> O2 + 4H^+ + 4e for which Eo = -1.23 volts. Of course using Eo means 1 M solutions an all that stuff and there is overvoltage to consider. In the real world you probably get some of several reactions going on at the same time or at least in short sequences, as GK as suggested,
You also could use graphite or carbon rods such as those from old worn out flashlight cells, specifically such as those that come from D or C cells. The why it won't work, at the anode, it is easier for Cu to go into solution (Cu ==> Cu+2 + 2e for which Eo = -.34 volts than it is to oxidize water
2H2O ==> O2 + 4H^+ + 4e for which Eo = -1.23 volts. Of course using Eo means 1 M solutions an all that stuff and there is overvoltage to consider. In the real world you probably get some of several reactions going on at the same time or at least in short sequences, as GK as suggested,
thanks, that pointed it all out
1 answer