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Potassium chlorate is an important potassium compound that can be used as an oxidizer, disinfectant, source of oxygen, and component in pyrotechnics and chemistry demonstrations. You can make potassium chlorate from common household bleach and salt substitute. The reaction is not particularly efficient, but it's something to keep in mind if you need potassium chlorate right away or just want to know how to make it.
Key Takeaways: Make Potassium Chlorate From Bleach and Salt Substitute
- Potassium chlorate is used as an oxidizer, disinfectant, and colorant (purple) in chemistry demonstrations and fireworks projects.
- While it's not the most efficient chemical reaction, it's simple to make potassium chlorate by boiling bleach, cooling it, and mixing in a saturated solution of salt substitute in water.
- The synthesis works because potassium from the salt substitute displaces sodium from the sodium chlorate made by boiling the bleach. The product is sodium chloride and potassium chlorate. Since potassium chlorate is not very soluble in water, it precipitates and may be collected by filtration.
Materials for Making Potassium Chlorate
You only need two ingredients to synthesize potassium chlorate:
- Chlorine bleach
- Potassium chloride (sold as a salt substitute)
- Filter paper or coffee filter
Take care to check the label on the salt substitute to make certain the ingredient is just potassium chloride. While salt substitute is potassium chloride, "lite salt" is a mixture of sodium chloride (table salt) and potassium chloride. The reason this project works is because potassium replaces sodium in sodium chlorate. Basically, you need to make certain you are supplying the potassium.
While it shouldn't be significant, keep in mind household bleach has a shelf life. If your bottle of bleach has been opened and stored a long time, it's a good idea to get a fresh one for the project.
Prepare Potassium Chlorate
- Boil a large volume (at least a half liter) of chlorine bleach, just until crystals start to form. Do this outdoors or under a fume hood, to avoid inhaling the vapor. Boiling bleach disproportionates sodium hypochlorite into sodium chloride and sodium chlorate.
3 NaClO → 2 NaCl + NaClO3
- As soon as crystals start to form, remove the bleach from heat and allow it to cool.
- In a separate container, prepare a saturated solution of potassium chloride by stirring potassium chloride into the water until no more will dissolve.
- Mix equal volumes of the boiled bleach solution and potassium chloride solution, taking care to keep solids from either solution out of the mixture. This is a substitution or single replacement reaction. The two products are separated based on solubility. Potassium chlorate will precipitate out, leaving sodium chloride in solution.
KCl + NaClO3 → NaCl + KClO3
- Cool the solution in the freezer to increase the potassium chlorate yield.
- Filter the mixture through filter paper or a coffee filter. Keep the solid potassium chlorate; discard the sodium chloride solution.
- Allow the potassium chlorate to dry before storing or using it. NurdRage has a video of the process if you'd prefer to see how it's done.
You can test the potassium chlorate in a simple chemistry demonstration:
- Purple Fire (shown) - Mix potassium chlorate and half as much sugar. Ignite the mixture either by applying a flame or adding a few drops of sulfuric acid (instant chemical fire).
- Dancing Gummi Bear - The candy is the source of the sugar in this demonstration. The vigorous reaction between the candy bear and the potassium chlorate makes the bear appear to dance in purple fire.
Other uses of potassium chlorate include safety matches, fireworks, disinfectants, pesticides, firearm primer, and to force plant blooming. It is also a good starting point to prepare oxygen gas or chlorine gas.
This is a project that should be performed with responsible adult supervision. Undiluted bleach can cause skin irritation and damage eyes and mucous membranes if splashed. Heating bleach should be done outdoors or under a fume hood, as irritating vapors are released. Finally, keep the potassium chlorate collected in this project away from heat or flame until you are ready to use it. It should be stored away from sulfuric acid and sulfur, as spontaneous ignition may occur.