A film of pure iron of such hardness as to resemble steel (hence the process is named "steel-facing") may be deposited on the face of an electrotype. The solution for the purpose is made as follows. Dissolve lib. of iron sulphate (green vitriol) in 1/2 gal. of rain water, and add a solution of ammonium carbonate until ail the iron has been precipitated. Wash the precipitate by pouring on water and allowing to settle, finally draining off all water possible. Then dissolve the wet precipitate in sulphuric acid to make a saturated solution, and use this as the depositing solution. As the solution has a tendency to become acid by working it, this must be corrected by using an anode plate of pure iron eight times larger than the electrotype to be faced, and placing a plate of platinum in the solution, attached to the iron anode, when the solution is not at work. Another solution, suitable for large operations, is made as follows. Dissolve 56 lb. of ammonium carbonate in 35 gal. of water. In this place a large anode of charcoal iron, and a small cathode of the same connected with a battery, and dissolve iron into the solution until a test strip of copper is nicely coated with iron in a few minutes.

Work this, and all other irou solutions, with a weak current - a battery of Daniell cells will do - keep the anode clean, and add free ammonium carbonate as required. The voltage necessary to work any solution and give best results must be found by experience always bearing in mind that iron solutions yield their metal in best condition at a low voltage. Iron solutions are also liable to change from atmospheric influences, the iron in solution being oxidised by contact with light and air. To minimise this trouble, keep the solutions covered. If a moderately thick coat of iron is desired the electrotype must be taken out every four or five minutes, and the face scrubbed in clean water, then replaced in the bath. When the coat is thick enough it should be well washed in hot water and rapidly dried, then oiled and brushed over with benzine. If not used at once it must be protected from rust by coating with a film of wax. The above process is applicable to metal articles other than electrotypes.