Definition of alkali in English:

alkali

nounPlural alkalis

  • 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’
    • ‘They resist most chemicals, including many acids, alkalis, oxidizing agents, and solvents.’
    • ‘Amides are hydrolysed to ammonium salts with catalysis by acids or alkalis.’
    • ‘Zinc is a fairly active metal that dissolves in both acids and strong alkalis.’
    • ‘Like semi-permanent dyes, permanent dyes are also alkalis.’
    • ‘Caustic alkalis react with the paint coating and loosen it from the surface.’
    • ‘It can withstand high temperatures and is resistant to many corrosive substances such as acids and alkalis.’
    • ‘Corrosives (mineral acids, alkalis, phenols) are in this category.’
    • ‘The high-density overlay protects the wood substrate from alkalis and water.’
    • ‘Nitriles can be decomposed by acids or alkalis to give the corresponding carboxylic acid or they can be reduced to give primary amines.’
    • ‘Tellurium reacts with both acids and some alkalis.’
    • ‘It accounted for acids and alkalis, for respiration and the smells of plants.’
    • ‘Soap is made by combining a fat source (either animal or vegetable) and an alkali in a chemical process known as saponification.’
    • ‘Platinum also dissolves in hot alkalis such as hot sodium hydroxide or potassium hydroxide.’
    • ‘Copper is a moderately reactive metal that dissolves in most acids and alkalis.’
    • ‘It combines with most non-metals at high temperatures and reacts with both acids and alkalis.’
    • ‘Concentrated acids and caustic alkalis should be handled with the greatest care.’
    • ‘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…’
    • ‘On contact, strong acids, alkalis, and heavy metals cause chemical burns.’
    • ‘Carboxylic acids also react with alkalis, or bases.’
    • ‘Chemically, aluminum will react with the alkalis in concrete and produce hydrogen bubbles.’
    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/