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 eight meshes to the inch; to these are added powdered sal-ammoniac, and sometimes flour 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. of sal-ammoniac to 1 cwt. iron turnings.

The following are recommended by Mr Molesworth : - Quick-setting Cement - 1 sal-ammoniac by weight.

2 flour of sulphur. 80 iron borings. Slow-setting Cement - 2 sal-ammoniac.

1 flour of sulphur. 200 iron borings. The latter cement being the best if the joint is not required for immediate use. In the absence of sal-ammoniac the urine of an animal may be substituted.

The cement will keep for a long time under water. Its efficacy depends upon the expansion of the iron in combining with the sal-ammoniac.

1 Spon.

2 Seddon.