Terephthalic acid, also known as p-phthalic acid, is the most productive binary carboxylic acid, mainly made from xylene, which is the main raw material for the production of polyester. It is a solid at room temperature. White needle crystal or powder. Soluble in alkaline solution, slightly soluble in hot ethanol, insoluble in water, ether, acetic acid and chloroform. Heating is not melting, above 300 ℃ sublimation.