IntelUsence and Miscellatieous Articles. 149 



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the same channel as the specimen of iridium above-mentioned*. 

 Rhodium is at least as fusible as iridium, both of the specimens 

 alluded to having been converted into fluid globules. That pro- 

 cured from Messrs. Johnson and Cock gave a globule weighing 

 ninety grains. On a second fusion it formed a perfect globule as 

 fluid as mercury ; and yet in congealing lost its brilliancy by be- 

 coming studded with crystalline facets all over its surface, excepting 

 the portion in contact with the support. The facets had the ap- 

 pearance of incipient spangles. The rapidity with which they were 

 formed seemed anomalous. The mass being split by a cold 

 chisel and viewed by a microscope, it appeared porous immediately 

 beneath the facets. When the mass was first fused, I found by the 

 gravimeter the specific gravity to be 11 '0, which coincides with the 

 observations of WoUaston. Yet by a careful trial made at the United 

 States mint by Mr. Eckfelt, after the second fusion and the forma- 

 tion of the facet, the specific gravity proved to be only 10'8. This 

 is sufficiently explained by the porosity above mentioned. In fact 

 the porosity to which rhodium and iridium are liable may render it 

 difficult to find specimens of precisely the same specific gravity. 



In sectility, malleability and hardness, rhodium did not appear to 

 differ much from iridium, but it is not of so pale a white as iridium. 

 The one has the pale white of antimony, the other the ruddy hue of 

 bismuth. 



Osmiuret of iridium, as existing in the native spangles associated 

 with platina ore, or as otherwise obtained, is far more difficult of 

 fusion than pure iridium. The propensity to assume the crystalline 

 form, and to adhere to it, is even greater in this alloy than in the 

 last-mentioned metal. On first exposure to the most intense heat 

 of the hydro-oxygen blowpipe some slight appearances of fusion 

 may be seen, and the spangles or grains may be made to cohere. 

 Nevertheless it yields very slowly, aijd requires an expenditure of 

 gas too great to be incurred unless it were for the purpose of once 

 well determining the question of its ultimate fusibility. This ob- 

 ject was obtained completely as respects a globule of 45 grains in- 

 weight. The specific gravity of this globule appeared to be 20*4, 

 but this result was evidently less than tliat whicii would have been 

 obtained had there not been some minute cavities, which, after 

 splitting the globule, were detected by a magnifier. 



The specific gravity of some large spangles of osmiuret of iridium 

 from South American ore was, by Dr. Boye, found to be 19*835. 

 That of some grains heavier but not so flat, presented to me by 

 Count Cancrine, was found to be 20'938. 



That the alloy of iridium with osmium should be more difficult to 

 fuse than pure iridium, leads to the inference that osmium must be 

 the most infusible of the metals, although, like carbon, very sus- 

 ceptible of combustion, and capable, like tliat infusible non-metallic 

 radical, of forming a volatile peroxide. Of course its liability to 

 oxidizement would render it impossible to fuse it by the hydro- 



* One other larger specimen from the same source has been fused since the 

 above was written. 



