2 sal-ammoniac; 1 flowers 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. The joints may be undone by heating the part to redness and jarring by hammer blows; paraffin or benzoline applied to the joint will sometimes assist.