What is pertaining to, or designating, an acid of sulphur obtained by leading hydrogen sulphide into a solution of sulphur dioxide; -- so called because it contains five atoms of sulphur called?

pentathionic — Pertaining to, or designating, an acid of sulphur obtained by leading hydrogen sulphide into a solution of sulphur dioxide; -- so called because it contains five atoms of sulphur. (Webster's 1913.)

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