Sodium Hydroxide vs Potassium Hydroxide: A comparison too caustic?

NaOH versus KOH. Caustic. In fact, too (two) caustic chemicals. Though both can be interchangeably used in a variety of situations, there are things which differentiate Sodium Hydroxide from Potassium Hydroxide. Apart from differences in chemical composition, there are a few similarities and differences in properties and usage too. NaOH or Sodium Hydroxide is used widely in industrial applications on account of its cheap availability, whereas Potassium Hydroxide finds more usage in domestic and other handcrafted applications. This article will draw a comparison chart on both the chemicals in terms of usage, properties and caustic ratio.

Sodium Hydroxide vs Potassium Hydroxide:
Sodium Hydroxide, now commonly called lye, is a caustic metallic base. Potassium Hydroxide, lye derived from wood ash (also called caustic potash) is a strong base used in niche applications. Both the chemicals have some common properties: both are caustic, corrosive and highly hazardous.

Pure sodium hydroxide is available in the form of granules, flakes, pellets or as a 50% saturated solution in drain cleaners. Potassium Hydroxide can be found in pure form by reacting sodium hydroxide with impure potassium. Often sold in the form of translucent pellets, it is highly soluble in methanol or ethanol. Sodium Hydroxide, on the other hand, exhibits only lower solubility in these solvents. Potassium Hydroxide is strongly exothermic, meaning it gives off heat when dissolved with water. Sodium Hydroxide, though not that exothermic, reacts vehemently with water to form lye solution. Both the chemicals should be stored in airtight containers as they are highly hygroscopic, meaning they absorb water in the air. A Sodium Hydroxide solution generally leaves yellow stain, while Potassium Hydroxide is white and translucent. Many concentrated aqueous solutions are called potassium lyes. Since the chemicals are hygroscopic, they do not dehydrate even at high temperatures when solid.

Caustic Soda vs Caustic Potash – Differences & Uses: Traditional lye got out of burnt wood is caustic potash or potassium hydroxide. Now, industrial lye has overtaken the traditional wood ash lye, making sodium hydroxide as the lye available in stores and with chemists. Both differ in weight and caustic potash is less hygroscopic than caustic soda. Since caustic soda is far more cheaper than caustic potash it finds use in a wide array of industrial and domestic applications.

Caustic Potash uses: Caustic potash has its own share of industrial applications and uses:

1. Caustic potash is used as a precursor to the preparation of several potassium compounds. Carbonate, cyanide, permanganate, phosphate, and various other silicates are prepared using KOH.

2. Potassium Hydroxide is also used in fertilizers on account of its high solubility

3. Soft soaps: Potassium Hydroxide is great for manufacturing soft soaps that tend to be more soluble or are often in liquid form. This is because sodium soaps are more easily solidified, compared to their potassium ones.

4. Electrolyte in alkaline batteries: Aqueous solution of potassium hydroxide is used as an electrolyte in batteries on account of its higher ratio of conductivity (compared to sodium hydroxide).

5. Degradative uses: Since potassium hydroxide is highly corrosive, it is used in labs for many specialized applications. In chemical synthesis, the preference of NaOH over KOH is decided by the desired solubility of the resulting salt. Unlike NaOH, potassium hydroxide is used as chemical cuticle removers.

Caustic soda uses: Sodium Hydroxide or lye has a variety of industrial and domestic applications. It is used in the following situations:

  • Soapmaking
  • Cleaning (in drain cleaners)
  • Petroleum refining
  • Aluminum production
  • Paper manufacture
  • Chocolate & cocoa processing
  • Food processing
  • Hair straightening
  • Dissolving animal carcasses (and human bodies)
  • Biodiesel manufacture

Analyzing both the chemicals, one cannot say that one is better than the other. Both Sodium Hydroxide and Potassium Hydroxide have their own share of industrial and domestic applications. Only thing is, both are caustic and hence should be handled with caution.

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This entry was posted on Saturday, January 25th, 2014 at 2:00 pm and is filed under Lye Facts, Uses of Lye. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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