













How to Synthesis
Potassium Perclorate
MAKING POTASSIUM PERCHLORATE

This proceedure is a "tried and true" method.  Unlike some rec.pyro postings, which are informational, or just  plain speculative, this proceedure WORKS.  I have used it myself to make my own supply of perchlorate -  until I decided to quit because I was making it far too fast to use.

This proceedure works well to make chlorates as well.  The  proceedure can be modified easily to make only chlorates. When using this proceedure to make perchlorate, it produces significant amounts of chlorate as a by-product.  This is because carbon rods are not highly efficient in converting  chlorate to perchlorate. Other anodes work better, but this proceedure was designed using easily available common    materials and supplies.

Carbon Rods

Get some carbon rods from the welding shop.  They are made by "arcair", and are 3/8" diameter by 12" long, and cost between  40 to 60 cents(US) each.  They are copper plated, and they are used     for a welding proceedure known as "gouging".

 Cut off the top of a plastic 1 gallon milk jug.  This is a good cheap source of containers for using in this proceedure.

Dissolve 1/2 cup of salt in 2 liters of warm water.  Put this in a small plastic container.  Cut out a piece of coffee can,   roughly 4" by 4" with a tab extending up to connect a wire to. The dimensions are not critical.  With a 6 volt battery charger, connect the minus (-) connector to the piece of coffee can.  Wrap some aluminum foil on the end of the carbon rod, to improve the electrical connection, and connect the plus (+) connector of the charger to it.

Turn on the charger, and let it run for about 20 minutes.  The copper will be removed from the rod.  If some still remains,  run it for a little longer till it is free of copper. Discard the salt water used to remove the copper. You can probably use a 12V charger, but the current may get too high, so you may need to reduce how much of the rod is being  etched at one time.
 
Electrolyte solution

Make a mixture of salt and potassium chloride solutions. Dissolve roughly 2 ounces (60 grams) of salt, and 8 ounces  (240 grams) of potassium chloride in 2 liters (just a bit more than 2 quarts) of hot water.  There is much room for  inaccuracy here, because the exact mixture is not absolutely        critical. At this point, it is good to add between 2 to 10 grams of either potassium chromate or dichromate.  While this is not  absolutely necessary, it helps improve how much perchlorate is finally produced.  The process will work without it, but  not quite as well.
NOTE: Potassium chloride can be obtained as several commonly available products, such as: dietary salt substitute,  ice melter (look at label for actual contents), and "muriate of potash" from farm and garden supply shops.   Hagenow Laboratories carries potassium dichromate.

The reason a mixture of salt and KCl is used, is two fold. First, salt is more easily electrolyzed than KCl, but after  it converts to chlorate (and perchlorate), it will tend form the potassium salt instead of the sodium salt.  The electrolysis tends to work on the sodium salt, while the final potassium  perchlorate forms, and due to it's poor solubility, tends to crystalize out of solution.  Secondly, the concentration of  KCl is chosen to help prevent chlorate from crystalizing out,       while being too high for the perchlorate to remain in solution, which causes it to crystalize out as it is created.  These concentrations may be varied, to compensate for different operating temperatures.  It was designed to operate at 40C, and will work fine above that temp, but below it, you might get  some chlorate crysatlizing out, in which case you might need to reduce the amount of KCl just a little. I have been using a little salt in my mixture, but someone could exclusively electrolyze KCl, without the addition of salt.  The purpose of the salt is to provide a sodium salt which is more  easily electrolyzed than the potassium salt.  It is NOT necessary, and will probably work well with only KCl.

BTW, chlorates are produced here as an intermediate chemical product.  Chlorates tend to be the predominant component around 1 1/2 to 2 days of operation.  Chlorate could be caused to     crystalize out during electrolysis if the concentration of KCl in the starting electrolyte solution is increased to nearly  saturation (about 21 ounces KCl/ with 2 ounces of salt). Although I have not concentrated on chlorate production, I would expect that you could actually run it for more than 2 days - possibly up to  4 or 5 days, and keep building up a layer of largely chlorate crystals on the bottom.  In that case, I would _GUESS_ that you could get around 2 pounds of chlorate after 5 days of operation.  

Electrolysis

     Using a coffee can for a source of steel, cut it out to form an inverted U shaped trough.  Insert it in the mixture of salt and KCl dissolved in water.  The (-) connector is connected to the steel.  The steel U trough (similar to a rain gutter, except upside down) is setting at an angle to increase the amount of surface area in contact with the liquid.  The carbon rod has some aluminum foil wrapped around the end of the rod, and the (+) connector is connected to it.  The rod is positioned within the U shaped trough - under it, without touching.  The charger is turned on, and he position & depth of the rod is adjusted to   get 8 to 12 amps of current.

NOTE: A setup with the electrodes running electricity through an electrolyte is called a "Cell".  This setup is commonly refered to as a cell throughout this description.

Let the liquid electrolyze for about 5 days continuously. Add water to make up for water lost during the process, and try to keep it roughly constant. A couple times a day, you will need to check the current level, and adjust the rod position to keep the current in the 8-12amp      range.  Mine has been running between 40 - 50C, but commercial  proceedures keep the temp just below 40C to reduce carbon rod  errosion.  The rods will gradually errode away, but if you use  a 6V charger, one rod will probably last for the full 5 days.You can also use higher voltage chargers, but you will probably  need to connect several electrolytic cells together to keep the voltage accross ONE cell to be about 6 volts.  If you use a 12 V charger, you will need 2 cells ( 12V/(6V per cell) = 2cells).  If you connect more than 1 cell in series, you may need to use a voltmeter to check the actual voltage accross each cell - because   it will change depending upon the resistance differences between  the cells, which can be adjusted by re-positioning the rods. The purpose for the U shaped trough cathode (-) electrode, is to cause the gas bubbles formed to generate a convection flow up   through the trough.  This causes the chemical products produced at each electrode to mix and react efficiently.  Other electrode geometries will work, some better, and others worse.  The key  is to cause the two electrodes to be very close to each other, and cause the chemical products to mix well to help form chlorate and perchlorates.  The WORST case situation is where the electrodes  are on opposite sides of the cell, causing the chlorine gas produced at the anode (+) to tend to bubble and escape  out of solution into the air.

Crystalization

     T he potassium perchlorate crystalizes out as it electrolyzes.  When you're done, you have a mixture of  black carbon, perchlorate, and some chlorate after you drain off the liquid.  I generally get a layer of perchlorate  crystals about 1 inch (2.5cm) thick on the bottom, which tends to be about 1 pound. Cool the liquid in a freezer to help increase the amount of perchlorate that is crystalized out, before draining the electrolyte liquid.  When draining the electrolyte, save it if you want to   re-electrolyze it to make even more perchlorate again. Load the crystals into a filter, and use boiling water to   dissolve the perchlorate out.  As it filters, the perchlorate forms  nice flat rhombic shaped (almost square) flakes that float out of solution.  You watch it as it cools, and watch for chlorate crystals,    which tend to look like clusters of cactus needles.  When they       start to form (well after the perchlorate has largely crystalized out), you drain the liquid, and add some room   temp water which is to be about 2 - 3 times the volume of the crystals you have in the container.  Shake them, and let it  stand overnight to dissolve any chlorate crystals.  Then  drain, wash (with ice cold water), and dry the crystals. You can purify them again by weighing the dried crystals, and adding enough water to dissolve the whole mass as if it was pure chlorate (i.e. 7g/100ml water)*.  Use hot water, and  then cool it down to room temp.  You might even need to cool get the perchlorate to begin to crystalize (it seems to super saturate commonly). You might be able to get it   started by adding a small amount of perchlorate dust as  crystal seeds - if you have some to start with.. Then wash   your crystals (with ICE COLD water), and dry them.  That will      help produce a higher purity product of perchlorate.  If you want to make a chlorate-free batch of perchlorate, repeat this  process again. It will be essentailly free of chlorate if you double crystalize it, and make certain you wash the crystals  several times with cold water.

       Example:  100 grams of crystals would require100grams/(7gm/100ml) = 14.3 (100 ml), or 1430 ml of water, or about 48 ounces.

      NOTE: When harvesting the crystals, a cotton cloth makes a  good filter.  I wear rubber gloves, and squeeze the excess liquid   from the crystals before & during washing them.  Squeezing      helps remove additional contaminants which are dissolved in the liquid that wouldn't otherwise be removed by  simple gravity filtering.  While this method loses very small crystaline particles, the loss tends to be very small   in comparison to the amount of crystals harvested. Perchlorate is very easy to make, but it takes a little   work.  The hardest ingredient to get is patience.      

