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XIII. On certain Mechanical Properties of Metals considered in relation to the 



Periodic Law. 



By W. CHANDLER ROBERTS-AUSTEN, F.R.S., Professor of Metallurgy in the Normal 

 School of Science and Royal School of Mines, South Kensington, Chemist and 

 Assayer of the Royal Mint. 



Received and Read March 15, 1888. 



[PLATE 18.] 



THE influence exerted by a small quantity of metallic or other impurity on a mass of 

 metal is shown by a remarkable series of phenomena the nature of which has hitherto 

 been but little studied, although the effect produced by the presence of such added 

 matter is widely recognised by metallurgists. There are many cases in which a small 

 quantity of impurity has so entirely altered the appearance and the physical properties 

 of a metal as to lead, in the absence of other evidence, to its being mistaken for a 

 distinct elemental substance. The valuable mechanical properties conferred upon 

 metals by associating them with small, but definite, amounts of other metals constitute 

 the main reason why metals devoted to industrial use are seldom employed in a state 

 of purity. A familiar instance of the influence of a small quantity of a metalloid on 

 a mass of metal is presented by the extraordinary change in the properties of pure 

 iron which attends the introduction into the metal of a small quantity of carbon. 

 There is no fact in metallurgy of which the importance is more widely recognised, and 

 when BERGMAN,* in 1781, experimentally demonstrated that the differences between 

 pure iron, steel, and cast-iron depend on the presence or absence of carbon, he expressed 

 his astonishment at the smallness of the amount of carbon capable of producing such 

 effects, and he stated that the explanation of the phenomenon presented a " difficulty 

 of difficulties " ; and the problem lias certainly not been solved in the century which has 

 elapsed since BERGMAN wrote. 



In other directions the evidence as to the importance of the action of traces of 

 impurity is just as strong. This is indicated by the fact, referred to by Sir HCSSEY 

 ViviAN.t that " one thousandth part of antimony converts first-rate ' best selected ' 



* 'De Analysi Ferri, Opnscnla Physica et Chemica,' by TOKBER.N BERGMAN, vol. 8, 1783: or French 

 translation (from the Swedish) : ' Analyse du Fer,' by M. GKIU.NOH. Paris, 1783. 

 t Lecture delivered at Swansea in 1J-80. 



2X2 30.10.88 



