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’
    • ‘It accounted for acids and alkalis, for respiration and the smells of plants.’
    • ‘Copper is a moderately reactive metal that dissolves in most acids and 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.’
    • ‘Like semi-permanent dyes, permanent dyes are also alkalis.’
    • ‘It can withstand high temperatures and is resistant to many corrosive substances such as acids and alkalis.’
    • ‘Amides are hydrolysed to ammonium salts with catalysis by acids or alkalis.’
    • ‘They resist most chemicals, including many acids, alkalis, oxidizing agents, and solvents.’
    • ‘Carboxylic acids also react with alkalis, or bases.’
    • ‘The high-density overlay protects the wood substrate from alkalis and water.’
    • ‘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.’
    • ‘Platinum also dissolves in hot alkalis such as hot sodium hydroxide or potassium hydroxide.’
    • ‘It combines with most non-metals at high temperatures and reacts with both acids and alkalis.’
    • ‘Nitriles can be decomposed by acids or alkalis to give the corresponding carboxylic acid or they can be reduced to give primary amines.’
    • ‘Concentrated acids and caustic alkalis should be handled with the greatest care.’
    • ‘Tellurium reacts with both acids and some alkalis.’
    • ‘Zinc is a fairly active metal that dissolves in both acids and strong alkalis.’
    • ‘Caustic alkalis react with the paint coating and loosen it from the surface.’
    caustic, corroding, eroding, erosive, abrasive, biting, mordant, burning, stinging
    View synonyms
    1. 1.1North American as modifier Alkaline.
      • ‘Oceanic island rocks form two major families based on mineralogy and petrography: those that form from tholeiitic basalts and those from alkali basalts.’
      • ‘Therefore, it is important that the high and low NHE3 groups do not differ with respect to daily food intake or dietary alkali load.’
      • ‘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.’
      • ‘On the stone soil, the whip antenna's efficiency is reduced 1.5-2.5 times (as compared to white alkali soil surfaces).’
      • ‘The dominant magma types are basalts and hawaiites, with lesser amounts of trachytes, quartz trachytes, alkali rhyolites and phonolites.’
      • ‘Femenia et al. reported the presence of such complexes in alkali extracts from lignified cauliflower stems.’
      • ‘A vast white alkali flat unrolled across the field of his dream, ringed with serrated purple mountains at the horizon.’
      • ‘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.’
      • ‘Those from the Yidun Terrane mostly lie in the field of alkali basalts.’
      • ‘This is especially crucial to document in alkali injuries.’
      • ‘The hydrothermal fluid introduced only small amounts of water and alkali elements (such as sodium and potassium).’
      • ‘Transformation of S. pombe was performed by treatment of cells with alkali cations.’
      • ‘Many such dikes in western Maine are classified as alkali diabase.’
      • ‘Also, Triassic rift-related alkali basalts are exposed in the adjacent Kocacli basin.’
      • ‘He disputes Lafarge's claim that ‘rogue employees’ were responsible for misreporting alkali levels in cement between September 2002 and December 2004.’
      • ‘You can't drink the water, but brine shrimp and alkali flies prosper in a mineral-rich California lake’
      • ‘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.’
      • ‘What little grass they found was encrusted with alkali soil, which only exacerbated the animals' thirst.’
      • ‘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.’
      • ‘Therefore, a relatively short period of alkali treatment was chosen.’

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


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’.