Ph3PO and the similar product POCl3 are both tetrahedral structure, Oxygen atoms is alkaline. The rigidity of the skeleton and the alkalescence Of the oxygen atomic, can both lead the three phenyl phosphine oxide to induce crystallize the compounds which hard to be crystallized by other methods, for the substances that containing acidic hydrogen, such as phenols are particularly effective, soluble in alcohol and benzene, slightly soluble in hot water, irritation.