1861.] 



Professor Faraday on Platinum. 



321 



WEEKLY EVENING MEETING, 



Friday, February 22, 1861. 



Sir Roderick I. Murchison, D.C.L. F.R.S. Vice-President, 

 in the Chair. 



Professor Faraday, D.C.L. F.R.S. 

 On Platinum. 



The discourse was founded on the recent investigations of MM. Henri 

 Ste-Claire Deville and H. Debray regarding the characters and con- 

 ditions of the platiniferous metals, and the new process of working the 

 ore which they have established on their results. Wherever platinum 

 occurs, it is usually, if not always accompanied by five other remark- 

 able metals ; namely, Ruthenium, Osmium, Iridium, Rhodium, and 

 Palladium : and in addition, by other substances, as iron, copper, gold, 

 silver, and sand. Being washed, the heavy particles are left as the 

 general ore of platinum ; this metal constituting by far the largest 

 part of the substances. 



The sJ5i metals, when obtained apart and purified, form two groups 

 of three each ; each group having an equivalent number very different 

 from that of the other group, as appears in this table : — 



Equivalent number, 95 • 5. 



1. Osmium 

 3. Iridium . 

 5. Platinum 



Spec. grav. 21-40 

 . . . „ 21-15 

 , . . „ 21-15 



Equivalent number, 53. 



2. Ruthenium 

 4. Rhodium . 

 6. Palladium 



Spec. grav. 11*3 

 . . „ 12-1 

 . . „ 11-8 



The three in the first group have the same equivalent number, and 

 nearly the same specific gravity ; but osmium takes the place of 

 platinum as the heaviest of bodies. The equivalent number of the 

 second group is alike for all, but it is little more than half that of the 

 former group. The specific gravity also of the group is little more 

 than half that of the former group : from which it* results that an 

 equivalent of any of these will have very nearly the same volume as an 

 equivalent of any one of the heavier group. 



'J'here are certain analogies between 1 and 2 ; 3 and 4 ; 5 and 6 ; 

 platinum is more like palladium than like the other metals. These 

 numbers also represent tlie order of fusibility. Osmium has not as 

 yet been fused ; the rest have, in the order given. Platinum appears 

 among them as a comparatively easily fusible metal. They are all 

 volatile at very high temperatures, even osmium disappearing whilst 

 the mass remains solid. 



