caseharden

I have a peculiar kind of steel which I cannot harden by fire and water, neither will it caseharden by prussiate of potash.

How to Caseharden Large Pieces of Steel.—A box of cast or wrought iron should be provided large enough to hold one or two of the pieces, with sufficient room all around to pack well with the casehardening materials, which may be leather scrap, hoof shavings, or horn shavings, slightly burned and pulverized, which may be mixed with an equal quantity of pulverized charcoal.

The same salt may be used to caseharden wrought iron.