Phosphorus pentachloride production. Laboratory apparatus for the synthesis of phosphorus pentachloride (PCl5) from phosphorus trichloride (PCl3, upper centre) and chlorine (Cl2, far left) gas. PCl5 is a white to pale yellow fine grained powder with a pungent odour. It is important in industry for the manufacture of phosphate compounds and as a chlorinating agent in the manufacture of pharmaceuticals and dyes.