What is (a) A salt of disulphuric or pyrosulphuric acid; a pyrosulphate. (b) An acid salt of sulphuric acid, having only one equivalent of base to two of the acid called?

disulphate — (a) A salt of disulphuric or pyrosulphuric acid; a pyrosulphate. (b) An acid salt of sulphuric acid, having only one equivalent of base to two of the acid. (Webster's 1913.)

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