on the alloys of steel. 261 
perceive, on the first action of the acid, the presence of the 
alloying metal. When this is platina, gold, or silver, a film 
of the metal is quickly formed on the surface of the acid. 
Of alloys of platina, palladium, rhodium, and iridium and 
osmium, a ready test is offered when the point is not to ascer- 
tain what the metal is, but merely whether it be present or 
not. For this purpose we have only to compare the action 
of the same acid on the alloy and on a piece of steel ; the 
increased action on the alloy immediately indicates the pre- 
sence of the metal ; and by the difference of action, which 
on experience is found to be produced with the different 
metals, a judgment may be formed even of the particular 
one present. 
The order in which the different alloys stand with regard 
to this action, is as follows : steel, cromium alloy, silver 
alloy, gold alloy, nickel alloy, rhodium alloy, iridium and 
osmium allov, palladium alloy, platina alloy. With similar 
acid the action on the pure steel was scarcely perceptible ; the 
silver alloy gave very little gas, nor was the gold much 
acted on. All the others gave gas copiously, but the platina 
alloy in most abundance. 
In connection with the analysis of these alloys, there are 
some very interesting facts to be observed during the action 
of acids on them, and perhaps none of these are more strik- 
ing than those last referred to. When the alloys are im- 
mersed in diluted acid, the peculiar properties which some of 
them exhibit, not only mark and distinguish them from com- 
mon steel, and from each other, but also give rise to some 
considerations on the state of particles of matter of different 
