uemura (Hive Bee)
09-27-01 05:58
No 217700
      Preparation of KClO3 (Potassiumchlorate)  Bookmark   

After uemuras summer break he is submitting two methods for the preparation of two valuable salts. This method shows how to make Potassium chlorate from OTC chemicals. KClO3 can be used for preparation of KMnO4, which is explained in onther thread.

KClO3 has been used in explosives. This is the main reason why it's watched and not sold to private persons. It is a strong oxidiser. It must kept very clean, it must be kept away from any organic substances as well from most other chemicals. ALL SUCH CHLORATE BASED MIXTURES ARE SENSITIVE TO FRICTION, AND  SHOCK, AND THESE BETTER BE AVOIDED.   The following two procedures are from the internet. Pyrotechnical de-tours have been removed to keep them nice and tidy.

Mol: 123 g/mol

Preparation (Procedure 1, using bleach powder)

Required Chemicals:
1200 g H.T.H (calcium hypochlorite 65%) 
220g Potassiumchlorid

Procedure 1:
In this reaction the H.T.H. (calcium hypo-chlorate CaC10) is mixed with water and heated with potassium chloride (salt substitute).  The  potasium chloride if prefered over sodium chlorite due to the easy crystallization of  the potassium chlorate.  This mixture will need to be boiled to ensure complete  reaction of the ingredients.
In a large pyrex glass or enameled steel container place 1200 g H.T.H. and 220 g  potassium chloride.  Add enough boiling water to  dissolve the powder and boil this solution.  A chalky substance (calcium  hydroxide?) will be formed.  When the formation of this chalky substance is no  longer formed the solution is filtered while boiling hot.  The potassium chlorate will drop  out or crystalize as the clear liquid left after filtering cools.  These  crystals are filtered out when the solution reaches room temperature.   The KClO3 can be easily recristallised from hot water. This will lead to a very pure product because of the high solubility of KClO3 in boiling water.

Preparation (Procedure 2, Electrolytical method from the Internet)

Required Chemicals:
454 G sodium chloride [1]
some muriatic acid
7g sodium dichromate [2]
9g barium chloride [3]

Procedure 2:

The major part  of the manufacture of this explosive from rock salt is the cell reaction where  D.C. current changes the sodium chloride to chlorate by adding oxygen by  electrolysis of a saturated brine solution.  The reaction takes  place as follows:
NaCl + 3H2O ----> NaClO3 + 3H2
In this reaction the sodium chloride (NaCl) takes the waters' oxygen and  releases its hydrogen as a gas.  This explosive gas must be vented away as  sparks or open flame may very well cause a tremendous explosion.  This type of  process or reaction is called a 'cell' reaction.  The cell should be constructed  of concrete or stainless steel.  I won't give any definite sizes on the cell's  construction because the size is relative to the power source.  This cell would  have to be large enough to allow the brine to circulate throughout the cell to  insure as uniform a temperature as possible.

The speed of the reaction depends on two variables.  Current density is a very  important factor in the speed of the reaction.  The advantages of high current  densities are a faster and more efficient reaction.  The disadvantages are that  cooling is needed to carry away excess heat and the more powerful power sources  are very expensive.  For small operations, a battery charger can be used  (automotive).  This is the example I will use to explain the cell's setup and  operation (10 amp 12 volt).  The current density at the anode (+) and cathode  (-) are critical.  This density should be 50 amps per square foot at the cathode  and 30 amps per square foot at the anode.  For a 10 amp battery charger power  source this would figure out to be 5 5/16" by 5 5/16" for the cathode.  The  anode would be 6 15/16" by 6 5/16".  The anode is made of graphite or pressed  charcoal and the cathode is made of steel plate (1/4").  These would need to be  spaced relatively close together.  This spacing is done with some type of  nonconducting material such as glass rods.  This spacing can be used to control  the temperature to some extent.  The closer together they are, the higher the  temperature.  These can be placed either horizontally or vertically although  vertical placement of the anode and cathode would probably be the ideal set up  as it would allow the hydrogen to escape more readily.  The anode would be  placed at the bottom  if placed horizontally in the cell so that the chlorine  released could readily mix with the sodium hydroxide formed at the cathode above  it.  As the current passes through, the cell chlorine is released at the anode  and mixes with the sodium hydroxide formed at the cathode.  Hydrogen is released  at the cathode which should bubble out of the brine.  This gas is explosive when  mixed with air and proper precautions should be taken.  PROPER VENTILATION MUST  BE USED WITH THIS OPERATION TO AVOID EXPLOSION.

Temperature control is left up to the builder of the cell.  The temperature of  the cell should be maintained at 56 degrees C during the reaction.  This can be  done by the circulation of water though the cell in pipes.  But the easiest way  would be to get an adjustable thermostatic switch adjusted to shut the power  source off until the cell cools off.  This temperature range could be from 59  degree shut off to a 53 degree start up.  An hour meter would be used on the  power source to measure the amount of time the current passes through the cell.   If the water cooling coil design appeals to the manufacturer and an easily  obtained cheap source of cool or cold water is available, this would be the  quickest design to use.  Again a thermostatic type arrangement would be used to  meter the cold cooling water through the cell.  The cooling coils would best be  made of stainless steel to overcome the corrosiveness of the salts although this  is not entirely necessary.  A thermostatic valve would be set to open when the  brine electrolyte was heated above approximately 58 degrees C.  Again this would  be the best and most efficient method and the waste heat could be used  relatively easily.

To run the cell, after the cell has been constructed and the concrete has been  sealed and has set and cured for several weeks, is very simple.  First to seal  the concrete I suggest Cactus Paint's C P 200 series, two component epoxy paint,  or an equivalent product.  To fill the cell place 454 G sodium chloride in the  cell (rock salt is excellent here).  Place four liters of distilled water into  the cell with the salt.  The liquid should cover the anode and the cathode  completely with room to spare.  Remember that some of the water will be used in  the reaction.  Thirty three grams of muriatic acid (hydrochloric), which should  be available at swimming pool supply stores or hardware stores, is then added to  the liquid in the cell.  Be careful when handling ANY acid!!!  Then seven grams  of sodium dichromate and nine grams of barium chloride is added.  The cell is  then ready to run if the plates are connected to their respective cables.  These  cables are best made of stainless steel (the most corrosion resistant  available).  The power supply is then hooked up and the cell is in operation.   The power is best hooked up remotely to lessen the chance of explosion.  Any  time the cell runs it will be making hydrogen gas. 


The steel plate cathode should be hooked to the negative side of the power  source and the anode hooked to the positive side.  Again these are hooked to the  power supply via stainless steel cables.  This cell is then run at the proper  temperature until 1800 amp hours pass through (amount per pound of sodium  chloride) the electrolyte.  The liquid in the cell is then removed and placed in  an enameled steel container and boiled until crystals form on liquid.  It is  cooled and filtered, the crystals collected being saved.  This is done twice and  the remaining liquid saved for the next cell run.  The process will become  easier as each run is made.  It is a good idea to keep records on yields and  varying methods to find out exactly the best process and yield.  To purify these  crystals place 200 grams in 100 ml distilled water.  Boil the solution until  crystals are seen on the surface.  Let cool and filter as before.  Save this  liquid for the next cell run.  These purified crystals are placed in a pyrex  dish and placed in the oven at 50 degrees C for two  hours to drive off all remaining water.

[1] The equivalent amount of Potassium chloride could be used as well.
[2] [3] These two are added to protect the electrodes. Should work without them.

Carpe Diem
(Hive Bee)
09-27-01 06:04
No 217703
      Re: Preparation of KClO3 (Potassiumchlorate)  Bookmark   

Referring to your method 1, a question... Hypochlorite and chloride give chlorine, don't they?

ClO- + H2O + Cl- --> Cl2 + 2OH-

(Hive Bee)
09-27-01 07:50
No 217726
      Re: Preparation of KClO3 (Potassiumchlorate)  Bookmark   

Uemura does'nt think any chlorine based on your reaction will develop. Method 1 is a dissociation rxn, details are not with Uemura at the moment. He will check.
For a nice movie (P+KClO3): www.pc.chemie.uni-siegen.de/pci/versuche/english/v44-26.html
(Hive Bee)
09-27-01 11:12
No 217805
      Re: Preparation of KClO3 (Potassiumchlorate)  Bookmark   

3OCl-+ heat --> ClO3 + 2Cl-

It's really easy, swic does it by getting some of the 10% sodium hypochlorite pool cleaner, boiling it down to about half its volume to get the chlorate, then adding the potassium chloride to get a crystallization. Only 3 grams of KClO3 dissolve in 100g H20 @ 0C. 32grams of NaCl  dissolve in 100g H20 @ 0C. This is great because you don't get that much sodium chloride impurities, and if you're worried you can just wash it with minimal loss. Don't know about Ca solubility though.
Only problem is swic doesn't know what it can be used for.
(Hive Bee)
09-27-01 13:22
No 217858
      Re: Preparation of KClO3 (Potassiumchlorate)  Bookmark   

Explanation for reaction of Procedure 1
From K.A.Hofmann&U.R.Hofmann, Anorganische Chemie, 1941
"Alkali- and earth-alkali salts of the chlorate azid can be prepared by saturation of the corresponding bases with chlorine and heating of theses solutions. The chlorine acts first on the prepared hypo-chlorite:

[1] Cl2 + H2O + KOCl <-> KCl + 2 HOCl

and the hypo-chlorite azid oxidizes its own salt

[2] 2HOCl + KOCl -> KClO3 + 2HCl

to the chlorate. The free HCl generates the free hypo-chlorite azid (HOCl), which again repeats [2] until the whole KOCl is used up. This happens quickly when the solution is heated. Very slowly a parallel reaction of the hypo-chlorite azid and the alkali chlorid takes place:

[3] KCl + 6 HOCl -> KClO3 + 3Cl2 + 3H2O

which improves the yield of the chlorate salt.
In former times a Ca(OH)2 suspension was saturated with chlorine and from the mix of CaCl2 and Ca(OCl)2 the KClO3 was precipitated with K2CO3. Today chlorates are produced by electrolyse of a chloride solution...
Carpe Diem
(Chief Bee)
09-27-01 13:31
No 217862
      Re: Preparation of KClO3 (Potassiumchlorate)  Bookmark   

Uemura: Where did you find this method?
(Hive Bee)
09-27-01 14:08
No 217881
      Re: Preparation of KClO3 (Potassiumchlorate)  Bookmark   

tanxs gnutella and a proper search string an ascii text file with some methods for the preparation of fireworks chemicals showed up. With lot of stupid and DANGEROUS errors in it. Anyway:
Prep 1 has been confirmed by Hofmann&Hofmann; Anorganische Chemie, 1941  (old books are great!) .
Prep 2 can also be found in Jander-Blasius, Lehrbuch der anal.u.prep.anorg.Chemie, Page 210
Carpe Diem