"Rust" cement, known also as cast iron cement, and by other names, is used for caulking the joints of cast iron tanks, pipes, etc. It is composed of cast iron turnings, pounded so that they will pass through a sieve of 8 meshes to the in.; to these are added powdered sal-ammoniac, and sometimes flowers of sulphur. The ingredients having been mixed are damped, and soon begin to heat. They are then again well mixed and covered with water. The exact proportions of the ingredients vary. A simple form is 1 oz. sal-ammoniac to 1 cwt. iron turnings. The following are recommended by Molesworth: -