Definition of alkali in English:



  • A chemical compound that neutralizes or effervesces with acids and turns litmus blue; typically, a caustic or corrosive substance of this kind such as lime or soda.

    Often contrasted with acid; compare with base
    • ‘Nickel has good resistance to corrosion in the normal atmosphere, in natural freshwaters and in deaerated nonoxidizing acids, and it has excellent resistance to corrosion by caustic alkalis…’
    • ‘Like semi-permanent dyes, permanent dyes are also alkalis.’
    • ‘The high-density overlay protects the wood substrate from alkalis and water.’
    • ‘Amides are hydrolysed to ammonium salts with catalysis by acids or alkalis.’
    • ‘It can withstand high temperatures and is resistant to many corrosive substances such as acids and alkalis.’
    • ‘Caustic alkalis react with the paint coating and loosen it from the surface.’
    • ‘Carboxylic acids also react with alkalis, or bases.’
    • ‘On contact, strong acids, alkalis, and heavy metals cause chemical burns.’
    • ‘Copper is a moderately reactive metal that dissolves in most acids and alkalis.’
    • ‘They resist most chemicals, including many acids, alkalis, oxidizing agents, and solvents.’
    • ‘Concentrated acids and caustic alkalis should be handled with the greatest care.’
    • ‘Zinc is a fairly active metal that dissolves in both acids and strong alkalis.’
    • ‘It combines with most non-metals at high temperatures and reacts with both acids and alkalis.’
    • ‘It accounted for acids and alkalis, for respiration and the smells of plants.’
    • ‘Platinum also dissolves in hot alkalis such as hot sodium hydroxide or potassium hydroxide.’
    • ‘Tellurium reacts with both acids and some alkalis.’
    • ‘Soap is made by combining a fat source (either animal or vegetable) and an alkali in a chemical process known as saponification.’
    • ‘Corrosives (mineral acids, alkalis, phenols) are in this category.’
    • ‘Chemically, aluminum will react with the alkalis in concrete and produce hydrogen bubbles.’
    • ‘Nitriles can be decomposed by acids or alkalis to give the corresponding carboxylic acid or they can be reduced to give primary amines.’
    caustic, corroding, eroding, erosive, abrasive, biting, mordant, burning, stinging
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Late Middle English (denoting a saline substance derived from the ashes of various plants, including glasswort): from medieval Latin, from Arabic al-ḳalī calcined ashes (of the glasswort, etc.) from ḳalā fry, roast.