With this knowledge at his disposal the iron-maker can work with his eyes open and so regulate his melt as to cause these various constituents to crystallize out as he wants them to.  Besides, he is no longer confined to the alloys of iron and carbon.  He has ransacked the chemical dictionary to find new elements to add to his alloys, and some of these rarities have proved to possess great practical value.  Vanadium, for instance, used to be put into a fine print paragraph in the back of the chemistry book, where the class did not get to it until the term closed.  Yet if it had not been for vanadium steel we should have no Ford cars.  Tungsten, too, was relegated to the rear, and if the student remembered it at all it was because it bothered him to understand why its symbol should be W instead of T. But the student of today studies his lesson in the light of a tungsten wire and relieves his mind by listening to a phonograph record played with a “tungs-tone” stylus.  When I was assistant in chemistry an “analysis” of steel consisted merely in the determination of its percentage of carbon, and I used to take Saturday for it so I could have time enough to complete the combustion.  Now the chemists of a steel works’ laboratory may have to determine also the tungsten, chromium, vanadium, titanium, nickel, cobalt, phosphorus, molybdenum, manganese, silicon and sulfur, any or all of them, and be spry about it, because if they do not get the report out within fifteen minutes while the steel is melting in the electrical furnace the whole batch of 75 tons may go wrong.  I’m glad I quit the laboratory before they got to speeding up chemists so.

The quality of the steel depends upon the presence and the relative proportions of these ingredients, and a variation of a tenth of 1 per cent. in certain of them will make a different metal out of it.  For instance, the steel becomes stronger and tougher as the proportion of nicked is increased up to about 15 per cent.  Raising the percentage to 25 we get an alloy that does not rust or corrode and is non-magnetic, although both its component metals, iron and nickel, are by themselves attracted by the magnet.  With 36 per cent. nickel and 5 per cent. manganese we get the alloy known as “invar,” because it expands and contracts very little with changes of temperature.  A bar of the best form of invar will expand less than one-millionth part of its length for a rise of one degree Centigrade at ordinary atmospheric temperature.  For this reason it is used in watches and measuring instruments.  The alloy of iron with 46 per cent. nickel is called “platinite” because its rate of expansion and contraction is the same as platinum and glass, and so it can be used to replace the platinum wire passing through the glass of an electric light bulb.