What is a compound radical, or unsaturated group, HO, consisting of one atom of hydrogen and one of oxygen. It is a characteristic part of the hydrates, the alcohols, the oxygen acids, etc called?

hydroxyl — A compound radical, or unsaturated group, HO, consisting of one atom of hydrogen and one of oxygen. It is a characteristic part of the hydrates, the alcohols, the oxygen acids, etc. (Webster's 1913.)

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