Abstract: An apparatus for treating a plurality of particles, such as ammonium sulfate, with a coating, such as a wax, to prevent caking of the particles. The apparatus includes a feed chute, a diffuser and an exit chute. An applicator is mounted adjacent a base of the diffuser for spraying the coating downwardly away from the diffuser into a predefined pattern. The exit chute includes a deflector for intersecting a curtain of particles falling from the diffuser and for redirecting the particles into the predefined pattern of the coating. A heating element is mounted to the deflector for maintaining a predetermined temperature of the deflector thereby preventing accumulation of the coating on the deflector.