Lucas Reagent Lucas reagent is a solution of anhydrous zinc chloride (Lewis acid) in concentrated hydrochloric acid. Lucas' reagent is used as a reagent to test alcohols of low molecular weight. Lucas reagent is used to classify alcohols in primary, secondary, and tertiary alcohols according to their reactivity. Lucas reagent is a solution mixture of hydrochloric acid and zinc chloride. To make the Lucas reagent, both of the reacting species, zinc chloride and hydrochloric acid, are taken in ... Lucas' reagent is a solution of zinc chloride in hydrochloric acid used to classify alcohols by their reactivity. Learn how the Lucas test works, its history, and its limitations. Lucas test is used to differentiate and categorize primary, secondary and tertiary alcohols using a solution of anhydrous zinc chloride in concentrated hydrochloric acid. This solution is commonly referred to as the Lucas reagent. What is the Lucas Test? Lucas reagent is a solution of zinc chloride and hydrochloric acid used to test and classify alcohols based on their reactivity. Learn how to prepare, use and handle Lucas reagent, and the mechanism of the substitution reaction it undergoes with alcohols.