Again, while iron, the carbon steels, and even the magnetic oxide of iron which contains only about 72 per cent of the metal, are strongly magnetic, manganese steel which has 85 per cent of iron is so non-magnetic that it is sometimes used in place of brass or bronze where an entirely non-magnetic material is required. The nickel steels with 24 per cent or more of nickel are also non-magnetic though both constituent metals, alone, are strongly attracted by the magnet. These are some of the things which make a logical classification of the iron family so difficult. Though derived from the steels which we knew and made from the same materials with the exception that a greater amount of one constituent, manganese, is added, or perhaps, in other cases, another element or two, the resulting alloys have markedly different and often contradictory properties. However, we must not be led astray. In all probability carbon is still the necessary constituent, but much less of it is needed to produce results when the other elements are present. There is no doubt, however, that in “manganese steel” or in “nickel,” “chrome,” “tungsten,” “silicon,” “vanadium,” “titanium,” and other alloy steels, the added element or elements exert very strong modifying influences, and sometimes obscure the influence of the carbon. In the first place, we better at once dispose of certain of these steels by terming the added element a “scavenger” only. Such usually are “titanium” and “aluminum” steels. These are generally ordinary carbon steels in which a very small amount of titanium or aluminum has been used to rid the alloy of certain gaseous or other deleterious elements. Upon analysis, steels so treated often show no trace of the element which has been added to do the work, all of it having passed into the slag, carrying with it the obnoxious substances, which, had they remained would have injured the quality of the steel. Manganese and silicon which were spoken of in the discussion of the Bessemer process as deoxidizing the metal, also exert just this same influence, though there is usually added of these enough that a certain percentage remains in the finished steel. Vanadium and titanium have a particular affinity for oxygen and nitrogen, and aluminum for oxygen. By chemically combining with these gases in the metal, and through possible other influence, they help to produce sound steel having very good physical properties. Vanadium, however, is much more than a “scavenger” as will be seen later on. Manganese Steel