What is of, pertaining to, or containing, sulphur and arsenic; -- said of an acid which is the same as arsenic acid with the substitution of sulphur for oxygen called?

sulphoarsenic — Of, pertaining to, or containing, sulphur and arsenic; -- said of an acid which is the same as arsenic acid with the substitution of sulphur for oxygen. (Webster's 1913.)

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