HYDRACRYLIC ACID is a syrupy liquid, which on dis tillation is resolved into water and acrylic acid, It is fl-hydroxypropionic acid, and is pre pared by acting with silver oxide and water on 0-iodopropionic acid, or from ethylene by the addition of hypochlorous acid, the addition product being then treated with potassium cyanide and hydrolysed by an acid. Hydracrylic aldehyde, is obtained as a colourless oil by heating acrolein with water.