1 822.] On the Alloys of Steel. 75 



than those last referred to. When the alloys are immersed 

 in diluted acid, the peculiar properties which some of them 

 exhibit, not only mark and distinguish them from common 

 steel, and from each other, but also give rise to some consider- 

 ations on the state of particles of matter of different kinds 

 when in intimate mixture or in combination, which may lead 

 to clearer and more perfect ideas on this subject. 



If two pieces, one of steel, and one of steel alloyed with pla- 

 tinum, be immersed in weak sulphuric acid, the alloy will be 

 immediately acted on with great rapidity and the evolution of 

 much gas, and will shortly be dissolved, whilst the steel will 

 be scarcely at all affected. In this case it is hardly possible 

 to compare the strength of the two actions. If the gas be col- 

 lected from the alloy and from the steel for equal intervals of 

 time, the first portions will surpass the second some hundreds 

 of times. 



A very small quantity of platinum alloyed with steel confers 

 this property on it : -yfa increased the action considerably ; with 

 -gl-Q and T n it was powerful ; with 10 per cent, of platinum it 

 acted, but not with much power ; with 50 per cent, the action 

 was not more than with steel alone ; and an alloy of 90 platinum 

 with 20 steel was not affected by the acid. 



The action of other acids on these alloys is similar to that 

 of sulphuric acid, and is such as would be anticipated : dilute 

 muriatic acid, phosphoric acid, and even oxalic acid, acted on 

 the platinum alloy with the liberation of more gas than from 

 zinc ; and tartaric acid and acetic acid rapidly dissolved it. 

 In this way chalybeate solutions, containing small portions of 

 protoxide of iron, may be readily obtained. 



The cause of the increased action of acids on this and 

 similar alloys, is, as the President of this Society suggested to 

 us, probably electrical. It may be considered as occasioned 

 by the alloying metal existing in such a state in the mass, that 

 its particles form voltaic combinations with the particles of 

 steel, either directly or by producing a definite alloy, which is 

 diffused through the rest of the steel ; in which case the 

 whole mass would be a series of such voltaic combinations : or 

 it may be occasioned by the liberation, on the first action of 

 the acid, of particles, which, if not pure platinum, contain, as 

 has been shown, a very large proportion of that metal, and 



