Preparation of Aspirin from Salicylic acid Aspirin Acetyl Salicylic acid also known as aspirin , is one of the most widely used medication to reduce fever and also used as pain killer . It is an acetyl derivative of Salicylic acid . It is white in colour , crystalline in shape, weakly acidic substance which melts at 135 Celsius . Theory Aspirin is synthesised through the reaction of Salicylic acid with acetic anhydride which turns salicylic acid's hydroxyl group into an acetyl group . A white , milky structure was obtained when Salicylic acid , acetic anhydride and sulphuric acid ( a catalyst ) were mixed . the mechanism of the reaction is In the first part of the experiment , Salicylic acid was heated so that it would melt and react with acetic anhydride . Sulphuric acid is added as a catalyst . it is strong acid so there are many available protons. the synthesis is acid catalysed. First there is a reversible reaction in which the the oxyge...