"alkalis" in the noun sense
1. base, alkali
any of various water-soluble compounds capable of turning litmus blue and reacting with an acid to form a salt and water
"bases include oxides and hydroxides of metals and ammonia"
2. alkali
a mixture of soluble salts found in arid soils and some bodies of water detrimental to agriculture
Source: WordNet® (An amazing lexical database of English)
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