Potassium Hydroxide

About This Product

Potassium hydroxide, also called caustic potash or KOH, is the potassium counterpart of caustic soda (CAS 1310-58-3, EC 215-181-3, formula KOH). It is made by electrolysing potassium chloride brine, and the resulting solution is either sold as liquid, commonly at 45–50%, or concentrated and solidified into flakes. Commercial flakes are typically 90% KOH minimum. The balance is mostly water of hydration rather than impurity, because fully anhydrous KOH is difficult and costly to produce. The main reason to choose potassium hydroxide over sodium hydroxide is the potassium salt it forms. Potassium soaps are softer and far more soluble than sodium soaps, which is why liquid soaps, soft soaps and many liquid detergents are saponified with KOH. The same solubility advantage applies to potassium carbonate, phosphates, silicates, acetate and formate, which are made from caustic potash for fertilisers, de-icing fluids and industrial uses. Potassium hydroxide is also a common catalyst for making biodiesel by transesterification, where low water and carbonate content help to limit soap formation, and it is the electrolyte in alkaline batteries. In cosmetics, small amounts adjust pH and neutralise acidic thickening polymers, and in cleaning products KOH provides alkalinity where a potassium system stays clear and liquid at higher concentrations. Food, pharmacopoeia and battery grades are separate products with tighter limits and their own documents; confirm the grade before using technical material in a regulated application. The parameters buyers agree are the KOH assay, potassium carbonate, chloride, iron and sodium content, sometimes with heavy metals for sensitive uses. Carbonate rises as the product absorbs carbon dioxide, so it indicates how well the material has been stored. Chloride is lower in material from membrane cells. Always calculate additions from the assay on the batch certificate of analysis, since 90% flakes deliver less alkali per kilogram than caustic soda. Potassium hydroxide is classified under CLP as causing severe skin burns and eye damage (H314), harmful if swallowed (H302) and possibly corrosive to metals (H290). Solid caustic potash ships as UN1813, POTASSIUM HYDROXIDE, SOLID, Class 8, and solutions as UN1814; it classifies under HS 2815.20. Confirm the packing group and classification in the safety data sheet for the supplied product. For imports into the EU or Great Britain, ask which company holds the REACH or UK REACH registration covering your import and use. KOH flakes are even more hygroscopic than caustic soda and will deliquesce in humid air, so keep containers tightly closed in a dry store away from acids, ammonium salts and aluminium, zinc or tin. Dissolve slowly into cold, stirred water, never the reverse, and wear goggles with a face shield, alkali-resistant gloves and protective clothing. When you enquire, state whether you need flakes or liquid, the grade, the KOH minimum and impurity limits, the pack size, your volumes, the destination and your Incoterms.