FAQs
How is potassium hydroxide different from sodium hydroxide?
Both are strong bases that dissociate completely in water, and they are often interchangeable for neutralization. Potassium hydroxide is more soluble in alcohols, which is why alcoholic KOH is standard for oil and fat titrations, and it is chosen when the potassium ion is wanted- for example, in soft-soap making and some battery electrolytes. KOH is also more expensive than NaOH.
Why buy KOH as a solution instead of solid pellets?
Solid potassium hydroxide is strongly deliquescent, absorbing water and carbon dioxide from the air so quickly that accurate weighing is difficult and pellets cake in the bottle. Ready-made solutions avoid this entirely, giving a known, stable concentration you can use immediately, which is especially important for standardized titrant solutions.
What is alcoholic (methanolic) KOH used for?
0.5 N potassium hydroxide in methanol is used to titrate acids in matrices where an aqueous titrant is unsuitable, most notably to determine the acid number and saponification value of oils, fats, and biodiesel. The alcohol dissolves the sample and keeps the reaction homogeneous, giving a sharp endpoint that aqueous KOH would not provide.
Why should KOH containers be kept tightly closed?
Besides limiting moisture uptake, keeping the container closed prevents the hydroxide from reacting with carbon dioxide in the air to form potassium carbonate. That reaction slowly lowers the effective base concentration, which would throw off titrations. A tightly sealed container preserves both the concentration and the titer of standardized solutions.
What metals and materials are incompatible with KOH?
Potassium hydroxide attacks aluminum, zinc, and tin, generating flammable hydrogen gas, so avoid those metals for containers and tools. It also reacts vigorously with acids. Use compatible glass or plastic labware and store it away from acids. The methanolic solution must also be kept away from ignition sources. See the SDS for the full list.
What first aid applies to a KOH burn?
KOH solutions cause severe, deep chemical burns. For skin or eye contact, immediately flush with copious water for an extended period and seek medical attention; alkali burns to the eye are especially serious. Wear splash goggles and gloves to prevent contact, and keep an eyewash and safety shower nearby. Follow the SDS first-aid section.
