The Lucas test is a test in alcohols that is conducted to test and differentiate between the types of primary, secondary or tertiary alcohol. It uses the differences in reactivity of hydrogen halides and the three classes or types of alcohol. In the reaction the hydrxy group is replaced by chlorine. The time it takes in the appearance of turbidity is used as a measure for determining the class of alcohol. A primary alcohol generally implies that no reaction will occur, secondary alcohols result in the solution turning cloudy after a period of three to five minutes and if the solution immediately turns cloudy it signifies that the alcohol present is tertiary, benzyl alcohol or allyl alcohol. This particular sort of test is generally conducted at room temperature.