Ordinary nickel steels commonly carry about 3¹⁄₂ per cent. nickel. “Highly nickeliferous steels carrying up to 40 per cent. nickel are used for special purposes where non-magnetic qualities, resistance to corrosion and, above all, no expansion or contraction, or any desired expansion or contraction, with change of temperature, is important.”[67] [67] Report of Royal Ontario Nickel Commission, 1917, p. 301. Non-ferrous nickel alloys have found extensive uses, and probably about 20 per cent. of the world’s production of nickel goes into them. By far the most important are those formed from nickel and copper. One, generally known as “cupro-nickel,” contains approximately 80 per cent. copper and 20 per cent. nickel and is used largely for bullet jackets and other munition purposes. Another, which has become well known under the trade name “Monel metal,” contains 29 per cent. copper, 67 per cent. nickel, about 2.5 per cent. iron, and a small amount of manganese. It is manufactured direct from the Sudbury matte. Monel metal is used chiefly where a strong non-corroding metal is needed, as, notably, in ship propellers. It is estimated that about 2 per cent. of the nickel production is used for electro-plating. To a large extent nickel plating prevents corrosion of the metal plated. Nickel is also used for storage batteries; for coinage; as a catalyser in the hardening of oils or fats (solid fats being used for soap making); for cooking utensils; and as a pigment for coloring ceramic ware. It is doubtful whether these last-named uses would take more than 3 per cent. of the world’s nickel production. Copper gives to steel properties somewhat similar to those given by nickel, notably increasing the tensile strength. Silicon also imparts similar properties to steel, increasing especially the toughness and tensile strength. A considerable proportion of chromium makes steel highly non-corroding. There is, however, nothing known that will take the place of nickel in special steels having a zero or a predetermined coefficient of expansion, such as “invar” or “platinite.” Nickel possesses extraordinary power in giving its white color to alloys of copper; hence its use in coinage. The other white metals that might be used in its place are less plentiful and more expensive. There is no other abundant metal or alloy having the good color, great strength and resistance to corrosion possessed by Monel metal and like alloys of nickel and copper. Nickel salts are used as substitutes for metals of the platinum group as catalysts in hardening oils and fats. CHANGES IN PRACTICE