The Regal Model 310/316 ammoniator is a vacuum-operated solution feed type, designed for mounting directly on an ammonia cylinder valve. The ammonia flow rate is manually adjusted. The ammoniator mounts on the cylinder valve by means of a positive, heavy duty yoke clamp. A highly efficient water operated, vacuum-producing ejector is close coupled with the ammonia solution diffuser. The assembly contains a back flow check valve. Ammonia gas flow rate is regulated by a spring opposed diaphragm regulator which is also the safety shut-off valve.