What is of, pertaining to, or designating, an unstable acid, H2S2O3, analogous to sulphuric acid, and formerly called hyposulphurous acid called?

thiosulphuric — Of, pertaining to, or designating, an unstable acid, H2S2O3, analogous to sulphuric acid, and formerly called hyposulphurous acid. (Webster's 1913.)

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