How to Mix Potassium Hydroxide in Water

Potassium hydroxide is the alkali form of a strongly electropositive metal. When potassium hydroxide dissolves in water, it rapidly forms ions that gather around themselves many molecules of water so that the ion charge spreads out over the entire surface area of those molecules. This reaction reduces charge density, producing stabilization. The more molecules of water that surround an ion (its "coordination number"), the lower the charge density becomes, and the greater the resultant stabilization. The stabilization energy releases into the solution, raising its temperature. Using improper laboratory technique for dissolving potassium hydroxide concentrates that heat into a small volume, resulting in dangerous super-heating.

Things You'll Need

• Potassium hydroxide pellets
• Distilled or deionized water
• Laboratory balance or scale
• Small laboratory scoop or other transfer implement
• Filter paper
• Plastic weighing dish (not aluminum)
• Rigid plastic beaker
• Graduated cylinder
• Magnetic stir plate and Teflon-coated bar magnet or glass stirring rod
• Laboratory gloves
• Goggles
• Paper face mask
• Lab jacket

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Instructions

The Correct Procedure

• 1

  Don a lab jacket, face mask, gloves, and goggles, making sure there are no gaps between the goggles and face.

• 2

  Place a filter paper on the pan of the balance or scale and place the plastic weighing dish on the paper. Set the weight to zero. Using the scoop, transfer potassium hydroxide pellets into the weighing dish in the correct quantity.

• 3

  Put the beaker on the hot plate and insert the Teflon bar magnet into the beaker. Pour about three-quarters of the total amount of water that will be used into the graduated cylinder and then transfer it into the beaker. Turn the stir plate on and set the speed to a moderately fast pace.

• 4

  Add the pellets very gradually into the water. Do not let many pellets settle to the bottom of the beaker and build up. Make sure most of them dissolve before adding more potassium hydroxide, which will avoid excessive heat buildup. Water temperature will rise considerably, but do not let it boil! If it gets close to boiling, wait a while before adding more potassium hydroxide. Otherwise, liquid may spatter. Potassium hydroxide solution produces caustic burns. Wait before adding more pellets as many times as necessary to maintain control over the process. Do this until all the potassium hydroxide has been added.

• 5

  Measure and add the rest of the water to the solution in the beaker while the stirring is still in progress. Allow the solution to cool before using. If it will be stored, do not use a glass receptacle, as potassium hydroxide solution slowly dissolves glass.