B.—CHEMISTRY. 47 
alloying elements, a striking example being that of Hadfield’s manganese 
steel, containing about 12 per cent. of the added metal, the effect of which 
is to delay the change to such an extent that with fairly rapid cooling the 
solid solution is perfectly preserved so that the steel is relatively soft, its 
chief peculiarity lying in the fact that any deformation brings about a 
partial change, producing the hard martensitic structure wherever there 
is flow. This is the reason for the extraordinary resistance of the alloy 
to abrasion, and for other properties which, being mechanical, lie outside 
the scope of the present discussion. 
Only a comparatively small number of metals will produce useful alloy 
steels. Those metals include, first, the immediate neighbours of iron, 
namely, cobalt and nickel, which resemble it so closely in most of their 
properties, and next the A members of the groups VI and VII of the 
periodic classification, chromium, molybdenum, tungsten and manganese. 
The next horizontal neighbour of nickel is copper, but it has only a very 
limited value as a constituent of steel, and its related elements are appar- 
ently of no use for this purpose. Uranium, the heaviest metal of the 
chromium group, does not alloy readily with iron, and the claims which 
have been made for its beneficial influence have not been confirmed. A 
small group of non-metals, all near neighbours of carbon, can enter into 
the composition of steels, namely boron, silicon, nitrogen and phosphorus, 
all of which have their uses in this connection. . Between the two groups 
lies the metal vanadium, which is very valuable when added in small 
quantities to steels. It would be of interest to study the two homologues 
of manganese, the metals having the atomic numbers 43 and 75, the 
discovery of which has been claimed quite recently, from this point of 
view if they should ever be found in sufficient abundance. The com- 
panions of the ferrous metals in group VIII, the platinum metals, do not 
appear to form alloy steels of any importance. An alloying element, 
a 
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to be of value, must be able to enter into solid solution in y- or a-iron or 
both, or to form a carbide which can do so. By varying the composition 
of alloy steels, and by subjecting them to different thermal treatments, 
a wide range of properties may be obtained, and the number of possible 
components being so large, it is clear that a very extensive field is offered 
for investigation. As a rule, only those alloys which lie within certain 
limits of composition have practical value, but dogmatism on this point 
is undesirable, and new and unexpected properties may be discovered 
