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Chris

Tue Apr 15 2008, 11:43PM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

It should have fine yield if you use a high density (like EDM grade) graphite anode and have a good system for combining the gases. Personally, I would use a sturdy glass reactor tube with a water cooling jacket. I would not use any metal parts in contact with the wet chlorine gas that comes from the cell, nor in contact with the wet HCl that is produced, if you want high purity. You may notice a greenish tint to commercial muriatic acid, no doubt due to impurities picked up from the industrial reactors which are made of metal. A UV pulse from a photo flash lamp should be enough to set off the reaction, producing HCl in a pulsed mode much like some kind of pulsejet. This should be simpler to regulate than a continuous combustion. I would use something like a polycarbonate tube for the cooling jacket so if the glass tube inside breaks, the shards will be contained. CCl4 from the anode is insoluble and inert so if any makes it through into your acid it should sink to the bottom. CO2 from the anode could be a contaminant too but I doubt you would care as this is only sparingly soluble. The main disadvantages of the electrolytic cell and HCl furnace are not that they are low yield, but that they will likely be frustratingly slow to get a large amount. Also, it isn't something you can cobble together in 10 minutes.

One thing that has not been mentioned yet is the need for a membrane or other good cell division with any kind of hydrogen-producing cell, especially if you aim to produce chlorine for HCl. In an undivided cell, chlorine that does not escape will tend to react with sodium and hydroxide ions to form sodium chlorate, and eventually sodium perchlorate. Tyvek (like used for house wrap and many other products) is the best membrane material that is easily obtained, but no membrane is perfect.

A better option yet (for the small scale/amateur, not necessarily for industry due to its lower electrical efficiency) is a two-chambered amalgam cell, if you can obtain a significant amount of mercury. In this type of cell, high purity sodium hydroxide is produced in-situ with hydrogen and chlorine gas. With a divider dipping down into the mercury pool, each half of the cell is entirely segregated, and the pool acts as the anode for one chamber and the cathode for the other chamber. Sodium is absorbed (alloyed) into the cathodic mercury from the anode chamber as metal, and pulled out of the anodic mercury into the cathode chamber (where no chloride ions are present) to react with water forming sodium hydroxide. Sodium hydroxide solution can be continuously pulled from the cathode chamber as sodium chloride is added to the anode chamber, while a volt meter across each can monitor the electrolyte balance between the chambers via relative cell voltage drop. CCl4 will also need removed somehow from the anode chamber (like by a collector right under the anode) as it would build up on top of the mercury pool and cut off current flow. The sodium hydroxide produced from such a cell inevitably has small traces of mercury contamination, and should probably be considered toxic, although it is very pure from an assay standpoint. For a better illustration/description:

Around here you can buy a gallon of 10M muriatic acid at hardware stores like ACE or Kenyon Noble for $5-$7, but it is not highly pure as I mentioned above. If your parents are not ok with you buying that, I can't imagine them being ok with you making your own gaseous HCl via a violent combustion process and bubbling it into solution. The only reason I have given any thought to an HCl furnace is the fact that muriatic acid may not be available to the public in stores for long, given the craze of government regulations that is going on due to the war on drugs. You can probably expect most useful chemicals to disappear from the shelves sooner or later, as many already have. If you can't buy it, you will need to make your own, plain and simple.

Backyard Skunkworks

Wed Apr 16 2008, 04:39AM

Registered Member #1262 Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451

Thanks for all the input, I don't really need huge yield and I highly doubt my parents will look twice if they see some new fabrication in my "lab". I dont think I wanna be messing with mercury in a home electrolysis cell, however I can have this thing running for long periods. As far as the reaction to get HCL gas I have heard its quite violent and exothermic, I've seen a few videos. To get around this I plan to react the gases in tiny quantities, I might opt for a pulse transformer sparking inside of the reactor tube, just to be sure it cooks off. As far as obtaining Hydrochloric at a hardware store I really wish I could however its just not an option at this time. When I get to college in a couple years I plan to start a small stockpile of all the good stuff (sulfuric, hydrochloric, lye etc...) before its banned in the name of "public safety" or nearly impossible to obtain like nitric and potassium nitrate.

My goal for an electrolysis cell is just a yield of maybe 10ml HCl (33% max) and 10ml NaOH (52% max) per hour of opperation. Maybe I should pick up some rock salt, or is it too impure to "electrolyze"?

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