The Collaborative International Dictionary
Prunella salt
Prunella \Pru*nel"la\, n. [NL., perhaps from G. br[ae]une quinsy, croup.] (Med.)
Angina, or angina pectoris.
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Thrush.
Prunella salt (Old Chem.), niter fused and cast into little balls.
Wiktionary
prunella salt
n. (context chemistry obsolete English) nitre fused and cast into little balls