TRANSACTIONS OF SECTION B. 589 



chemistry from the sciences of physics and mechanics. lie has, in fact, no ]onf,'er to 

 deal merely with atoms and molecules, hut with the influence of mass. As Ostwald 

 points out, we are reminded that many chemical processes are reciprocating so that 

 the original bodies may be obtained from the product of the reaction. The result 

 of such opposed processes is a state of chemical EauiLiERiuM, in which both the 

 original and the newly-formed substances are present in definite quantities that 

 remain the same so long as the conditions, more especially temperature and pres- 

 sure, do not undergo further change. Again, in very many metallurgical processes, 

 reactions are rendered incomplete by the limitations imposed by the presence of 

 bodies which cannot be speedily eliminated from the system, and the result may 

 be to greatly retard the completion of an operation. The time has come when the 

 principles of dynamic chemistry must be applied to the study of metallurgical pro- 

 blems if they are to be correctly understood, and it is, moreover, necessary to 

 remember the part played by the surface separating the different aggregates in 

 contact with one another. When, for instance, a reaction has to take place accom- 

 panied by the evolution of gas, there must be space into which the gas can pass. 

 The rate, therefore, at which change takes place will obviously depend on the state 

 of division of the mass. 



One of the most remarkable points in the whole range of chemistry is the action 

 engendered between two elements capable of reacting by the presence of a third 

 body. It may be, and this is the most wonderful fact of all, that merelj' a trace 

 of a third body is necessary to induce reaction, or to profoundly modify the struc- 

 ture of a metal. H. Le Ghatelier and Mouret have pointed out that in certain 

 cases it is inaccurate to say that the third body causes the reaction to take place, 

 because, after it has destroyed the inter-molecular resistances which prevented the 

 reaction taking place, the third body ceases to intervene. This is apparently the 

 case when platinum sponge effects the union of oxygen and hydrogen, or conveisely, 

 when very hot platinum splits up water vapour into its constituent gases. Future 

 investigation will, it is to be hoped, show whether the platinum does not e.\ert 

 some direct action in both cases. We can no longer neglect the study of such 

 questions from the point of view of their practical application. The manufacture 

 of red-lead presents a case in point. In ' dressing' molten lead, the oxidation of the 

 lead is greatly promoted by the presence of a trace of antimony, and conversely, in 

 the separation of silver from molten lead, by the aid of zinc, H. Eoessler and 

 Endelmanu have recently shown that aluminium has a remarkable effect in pro- 

 tecting the zinc from loss by oxidation, and, further, the presence of one-thousandth 

 part of aluminium in the zinc is sufficient to exert this protecting action on that 

 metal. I am satisfied that if our metallurgists are to advance their industrial 

 practice, they must, if I may use such an expression, persistently think in calories, 

 and not merely employ the ordinary atomic ' tools of thought.' They will then 

 be able to state what reactions can, under given conditions, take place ; to indicate 

 those which will be completed ; and to avoid those that are impracticable. 



In France, the country of so many great metallurgists, men like Le Ghatelier 

 and Ditte are doing admirable service by bringing the results of the labours and 

 teaching of St. Claire Deville within the range of practical men. And if I do not 

 refer more specifically to their work it is for want of space and not of appreciation, 

 but a few simple cases of reversible actions will perhaps make the subject clear. In 

 the blast-furnace the main reducing agent, carbonic oxide, is produced from the solid 

 fuel by the reaction CO., -i- C = 2 CO, a reaction which is theoretically impossible 

 because it is endothermic, and wotdd be attended by absorption of heat. But heat 

 external to the system intervenes, and acts either by depolymerising the carbon 

 into a simpler form which can combine with oxygen of the CO., with evolution of 

 heat, or by dissociating carbonic anhydride sets oxygen free which combines with 

 the carbon. Reduction of oxide of iron in the blast-furnace is mainly effected by 

 carbonic oxide according to the well-known reaction 



Fe^Oj + SCO = 2Fe + SCO^. 



But the gas issuing from a blast-furnace contains carbonic oxide, an important 

 source of heat. The view that this loss of carbonic oxide was due to the fact that 



