Here is a link to a previous thread explaining the chemical reaction
http://www.mtfca.com/discus/messages/50 ... 1431383875
By Michael Pawelek Brookshire, Texas on Monday, May 11, 2015 - 07:00 am:
The electrolytic rectifier was fairly common from the turn of the century
through the twenties. A large portion of them were used in communications,
i.e. telegraphy, telephony, and radio. It was replaced by the more robust,
maintenance-free selenium rectifier and vacuum tube rectifier. The other
"tin-like" electrode you mention is aluminum. As far as the electrolyte
(secret liquid) goes, several things will work. I used ammonium chloride (sal
ammoniac) in my 'B' radio supply. The following is a quote from a 1943 Coyne
Electrical School text:
"The electrolytic rectifier is also limited to small capacities, due to its
low efficiency and general tendency to heat up under load because of the large
resistance losses which take place within the rectifier itself. This type of
rectifier consists of a jar containing a strong solution of ammonium
phosphate, sodium phosphate, or just a mixture of water and common borax. In
this solution are immersed a plate of either lead, carbon, or iron, and one of
aluminum. The electrolytic action which is set up between the surface of the
aluminum electrode and the electrolyte solution will allow the current to flow
from the solution into the aluminum, but will immediately build up a very high
resistance film when the current is reversed and tries to flow from the
aluminum into the electrolyte."
A common substance that will also work in solution is sodium bicarbonate
(baking soda). I've never tried it so I don't know how efficient it is.
Ammonium phosphate might be available at your local Agway sold as fertilizer.
(Tri)sodium phosphate is a common cleaning agent and is somewhat caustic.
Borax should be easy to find. If you fire that thing up, be careful not to
overheat the jars -- it doesn't take long under high-current conditions.