Definition of alkali in English:

alkali

noun

  • A compound with particular chemical properties including turning litmus blue and neutralizing or effervescing with acids; typically, a caustic or corrosive substance of this kind such as lime or soda.

    Alkalis release hydroxide ions (OH⁻) when dissolved in water. Any solution with a pH of more than 7 is alkaline

    ‘flint is not subject to chemical weathering except by strong alkalis’
    Often contrasted with acid and base
    mass noun ‘the reaction is followed by measuring the concentration of alkali at various times’
    • ‘Carboxylic acids also react with alkalis, or bases.’
    • ‘The high-density overlay protects the wood substrate from alkalis and water.’
    • ‘Tellurium reacts with both acids and some alkalis.’
    • ‘Amides are hydrolysed to ammonium salts with catalysis by acids or alkalis.’
    • ‘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…’
    • ‘Platinum also dissolves in hot alkalis such as hot sodium hydroxide or potassium hydroxide.’
    • ‘It can withstand high temperatures and is resistant to many corrosive substances such as acids and alkalis.’
    • ‘Concentrated acids and caustic alkalis should be handled with the greatest care.’
    • ‘It combines with most non-metals at high temperatures and reacts with both acids and alkalis.’
    • ‘Copper is a moderately reactive metal that dissolves in most acids and alkalis.’
    • ‘It accounted for acids and alkalis, for respiration and the smells of plants.’
    • ‘They resist most chemicals, including many acids, alkalis, oxidizing agents, and solvents.’
    • ‘Nitriles can be decomposed by acids or alkalis to give the corresponding carboxylic acid or they can be reduced to give primary amines.’
    • ‘Soap is made by combining a fat source (either animal or vegetable) and an alkali in a chemical process known as saponification.’
    • ‘Chemically, aluminum will react with the alkalis in concrete and produce hydrogen bubbles.’
    • ‘Like semi-permanent dyes, permanent dyes are also alkalis.’
    • ‘Corrosives (mineral acids, alkalis, phenols) are in this category.’
    • ‘On contact, strong acids, alkalis, and heavy metals cause chemical burns.’
    • ‘Caustic alkalis react with the paint coating and loosen it from the surface.’
    • ‘Zinc is a fairly active metal that dissolves in both acids and strong alkalis.’
    caustic, corroding, eroding, erosive, abrasive, biting, mordant, burning, stinging
    View synonyms

Origin

Late Middle English (denoting a saline substance derived from the ashes of various plants, including glasswort): from medieval Latin, from Arabic al-qalī ‘calcined ashes (of the glasswort etc.)’, from qalā ‘fry, roast’.

Pronunciation

alkali

/ˈalkəlʌɪ/