Gallic acid propyl referred to PG. White to light brown crystalline powder or white needle-like micro-crystalline. Odorless, slightly bitter, odorless solution. PG is insoluble in water, slightly soluble in cottonseed oil, peanut oil, pig fat. The 0.25% solution of the PH value of 5.5 or so. Propyl gallate relatively stable, except copper, iron and other metal ions forming reaction, becomes purple or dark green, hygroscopic, light instability, the occurrence of decomposition, high temperature is poor.