What is the difference between sodium hydroxide and potassium hydroxide flakes KOH?

1. Differences in physical and chemical properties

1) Potassium hydroxide flakes KOH is a white rhombic crystal, and the industrial product is white or light gray flakes. Relative density is 2.044 at 20℃. Melting point 360.4℃. Boiling point 1320～1324℃. It is easily soluble in water, and releases a large amount of heat of dissolution when dissolved. It has strong water absorption, can absorb water and dissolve in the air, and absorbs carbon dioxide to gradually become potassium carbonate. Soluble in ethanol and slightly soluble in ether. It has extremely strong alkalinity and corrosiveness, and its properties are similar to caustic soda.

2）Sodium hydroxide is a colorless and transparent crystal with a relative density of 2.130. Melting point 318.4℃. Boiling point 1390℃. Sodium hydroxide has two types: solid and liquid. In pure solid state, it has a white appearance, and there are blocks, flakes, rods, granules, and it is brittle; in pure liquid state, it has a colorless and transparent liquid appearance. Sodium hydroxide will completely decompose into sodium ions and hydroxide ions when dissolved in water, so it has strong alkalinity. It is easy to deteriorate into sodium carbonate in the air; it can react with aluminum to generate hydrogen.

The common point is both two are highly corrosive and cannot come into contact with metal containers. They are also easy to deliquesce and should be kept sealed.

2. Differences in chemical analysis: Although potassium hydroxide flakes KOH and sodium hydroxide can be used interchangeably. However, there are some applications where the two cannot be used interchangeably. Sodium hydroxide is more hygroscopic than potassium hydroxide flakes KOH, so potassium hydroxide flakes KOH is often used in chemical analysis; if used as a desiccant, sodium hydroxide is generally used.

3. Differences in saponification reactions: potassium hydroxide flakes KOH produces weak soap, while sodium hydroxide produces hard soap.

4. Price differences: The market price of potassium hydroxide flakes KOH is much higher than that of sodium hydroxide. 

5. Differences in the application of the two:

1) Potassium hydroxide is used as an analytical reagent, saponification reagent, desiccant and moisture absorbent; used to make oxalic acid and various potassium salts; electroplating, engraving, lithography, etc.; also used for printing and dyeing, bleaching and mercerization, and is used in large quantities as the main raw material for the manufacture of artificial fibers and polyester fibers, and is also used to make melamine dyes.

2) Sodium hydroxide is used in the production of paper, soap, dyes, rayon, metal smelting, petroleum refining, cotton fabric finishing, coal tar product purification, as well as food processing, wood processing and machinery industry.

In summary, potassium hydroxide flakes KOH and sodium hydroxide differ in physical and chemical properties, applications, prices, etc., and you can choose the appropriate product according to your specific needs.