potassium hydroxide sodium hydroxide chemical chemistry

Side by Side Comparison: Potassium Hydroxide and Sodium Hydroxide – Similarities, Differences and Use Cases

Sometimes choosing the right chemical for your project can get tricky. The chemical world is vast and with so many similar compounds, sometimes you have a choice between a few chemicals that will work for your project. But which one will work best?

Two compounds that are often equally viable options are potassium hydroxide and sodium hydroxide. If you are stuck between these two compounds, this article will help you determine which will be the best choice for you.


Potassium hydroxide (KOH) and sodium hydroxide (NaOH) are alkali metal hydroxides. Like most compounds, potassium hydroxide and sodium hydroxide have common names you are likely familiar with. You may know sodium hydroxide as lye or caustic soda; while potassium hydroxide is commonly known as potash.


Uses of Potassium Hydroxide & Sodium Hydroxide

Potassium hydroxide and sodium hydroxide are used in many manufacturing applications. They are very similar—more on that in a moment—and can often be used in the same applications.


In manufacturing soaps, both potassium hydroxide and sodium hydroxide are used in saponification, a process that converts fats into soap. Likewise, both compounds can be used to make biodiesel. Potassium hydroxide and sodium hydroxide react with triglycerides in the same way by dissolving the triglycerides, which allows methanol to bond with fatty acids, the foundation of biodiesel fuel. And both are approved by the FDA as a thickening agent and stabilizer in processed foods.


Despite their similarities, there are a few uses in which you can not swap one for the other. Potassium hydroxide is used as an electrolyte in alkaline batteries. Meanwhile, sodium hydroxide is used in water purification.


But to get a better understanding of when to choose one over the other, you need to understand the similarities and differences between potassium hydroxide and sodium hydroxide.


Similarities of Potassium Hydroxide & Sodium Hydroxide 

Potassium hydroxide and sodium hydroxide are both highly corrosive, strong bases. Both are formed by ionically binding an alkali metal to a hydroxide group. Of all the compounds in the hydroxide group, potassium hydroxide and sodium hydroxide are the most chemically similar.


Their strong chemical similarity allows them to easily stand in for each other in a number of uses. Accordingly, their chemical reactions are remarkably similar. Because potassium hydroxide and sodium hydroxide are both strong bases, they react to water by releasing heat. So they are both highly exothermic.


Their chemical similarity lends to a physical similarity as well. In solid form, they are both white powder or flakes. When dissolved they can each be used as an aqueous solution.


Differences in Potassium Hydroxide & Sodium Hydroxide

Though sodium hydroxide and potassium hydroxide are very similar, they are fundamentally different. To begin with, potassium and sodium each contribute a different number of protons. Sodium brings in 11 protons, while potassium donates 19. Likewise, the metal in sodium hydroxide is lighter than that of potassium hydroxide. This contributes to their vastly different atomic weights of 39.997 g/mol and 56.106 g/mol respectively.


But their differences actually start all the way down at the molecular level. Potassium hydroxide is slightly smaller than sodium hydroxide which means it cuts through oil molecules faster than sodium hydroxide. This makes potassium hydroxide a great choice for soaps that need to remove caked-on oil.


Their reactions are slightly different as well. Both sodium hydroxide and potassium hydroxide release heat when they react with water. But the chemical makeup of potassium hydroxide creates slightly less heat than sodium hydroxide when exposed to water.


Due to production costs, potassium hydroxide is generally more expensive than sodium hydroxide. Sodium hydroxide is produced using sodium chloride, otherwise known as plain table salt. Whereas potassium chloride, a more costly compound, is used to produce potassium hydroxide.


There are a lot of considerations when choosing between potassium hydroxide and sodium hydroxide. Contact us to speak to our team of knowledgeable in-house chemists who can provide technical assistance based on your project specifications.


Or, if you have already determined the perfect compound for your project, browse our extensive online catalog and have the perfect chemical for your project shipped right to you.



Noah Chemicals is dedicated to providing clients the purest chemicals. Buy these chemicals directly from our massive online catalog. To speak with a qualified chemist about custom chemicals and bulk ordering contact us today!




POTASSIUM HYDROXIDE, 99.9% pure, flake, KOH






SODIUM HYDROXIDE, 50% SOLUTION, Reagent, (Caustic Soda), NaOH


SODIUM HYDROXIDE, 99% pure, beads, (Caustic Soda), NaOH


SODIUM HYDROXIDE, 99.99% pure, pellets, (Caustic soda), NaOH


SODIUM HYDROXIDE, ACS Reagent, pellets, (Caustic Soda), NaOH

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