Definition of alkali in English:



  • 1A 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:

    ‘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’
    • ‘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.’
    • ‘Concentrated acids and caustic alkalis should be handled with the greatest care.’
    • ‘They resist most chemicals, including many acids, alkalis, oxidizing agents, and solvents.’
    • ‘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…’
    • ‘The high-density overlay protects the wood substrate from alkalis and water.’
    • ‘On contact, strong acids, alkalis, and heavy metals cause chemical burns.’
    • ‘Copper is a moderately reactive metal that dissolves in most acids and alkalis.’
    • ‘Caustic alkalis react with the paint coating and loosen it from the surface.’
    • ‘Corrosives (mineral acids, alkalis, phenols) are in this category.’
    • ‘Like semi-permanent dyes, permanent dyes are also alkalis.’
    • ‘Amides are hydrolysed to ammonium salts with catalysis by acids or alkalis.’
    • ‘Soap is made by combining a fat source (either animal or vegetable) and an alkali in a chemical process known as saponification.’
    • ‘Zinc is a fairly active metal that dissolves in both acids and strong alkalis.’
    • ‘It accounted for acids and alkalis, for respiration and the smells of plants.’
    • ‘Chemically, aluminum will react with the alkalis in concrete and produce hydrogen bubbles.’
    • ‘Platinum also dissolves in hot alkalis such as hot sodium hydroxide or potassium hydroxide.’
    • ‘Carboxylic acids also react with alkalis, or bases.’
    • ‘It combines with most non-metals at high temperatures and reacts with both acids and alkalis.’
    • ‘It can withstand high temperatures and is resistant to many corrosive substances such as acids and alkalis.’
    caustic, corroding, eroding, erosive, abrasive, biting, mordant, burning, stinging
    View synonyms
    1. 1.1North American [as modifier] Alkaline.
      • ‘Femenia et al. reported the presence of such complexes in alkali extracts from lignified cauliflower stems.’
      • ‘The dominant magma types are basalts and hawaiites, with lesser amounts of trachytes, quartz trachytes, alkali rhyolites and phonolites.’
      • ‘The hydrothermal fluid introduced only small amounts of water and alkali elements (such as sodium and potassium).’
      • ‘Therefore, a relatively short period of alkali treatment was chosen.’
      • ‘These smaller volumes of melt are rich in elements such as sodium and potassium (alkali metals), which are the first elements to move into the melt; the resulting rocks are called alkali basalts.’
      • ‘Those from the Yidun Terrane mostly lie in the field of alkali basalts.’
      • ‘You can't drink the water, but brine shrimp and alkali flies prosper in a mineral-rich California lake’
      • ‘He disputes Lafarge's claim that ‘rogue employees’ were responsible for misreporting alkali levels in cement between September 2002 and December 2004.’
      • ‘Also, Triassic rift-related alkali basalts are exposed in the adjacent Kocacli basin.’
      • ‘Additionally, clinically, if CO2 tensions venture into the range of 80-100 mm Hg in critically patients, the use of alkali therapy is generally mandatory.’
      • ‘Many such dikes in western Maine are classified as alkali diabase.’
      • ‘What little grass they found was encrusted with alkali soil, which only exacerbated the animals' thirst.’
      • ‘For the first few days, the country presented picturesque timbered bottomlands and rolling prairie, but slowly it changed to a rocky landscape littered with buffalo bones and stagnant pools of undrinkable alkali water.’
      • ‘Therefore, it is important that the high and low NHE3 groups do not differ with respect to daily food intake or dietary alkali load.’
      • ‘This is especially crucial to document in alkali injuries.’
      • ‘A vast white alkali flat unrolled across the field of his dream, ringed with serrated purple mountains at the horizon.’
      • ‘On the stone soil, the whip antenna's efficiency is reduced 1.5-2.5 times (as compared to white alkali soil surfaces).’
      • ‘Oceanic island rocks form two major families based on mineralogy and petrography: those that form from tholeiitic basalts and those from alkali basalts.’
      • ‘Transformation of S. pombe was performed by treatment of cells with alkali cations.’
      • ‘He watches flies crawl onto heat-softened flypaper and wave their gummy limbs in torturous gestures toward escape, captive, his mother suggests, as she and he are on this alkali flat.’


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.