148 Intelligence and Miscellaneous Articles, 



a peculiar degree of energy exists. At a certain point of the process 

 a reaction took place sufficiently explosive to throw a portion of the 

 metal, in globules, off from the support. One of these, about twice 

 as large as the head of a common brass pin, proved to be hollow. 

 By prolonged and repeated fusion the metal became more compact 

 and more fusible. 



Fused iridium has nearly the grain of soft cast steel, with the pale 

 whiteness of antimony, and appears to be susceptible of a fine polish. 

 Although as hard as untempered steel, it is somewhat sectile, since, 

 when split by means of a cold chisel, the edge penetrated about the 

 eighth of an inch before a division was effected. By light ham- 

 mering a corner was flattened without fracture, although under 

 heavier blows the mass cracked. I infer that although nearly un- 

 malleable and very hard, iridium may be wrought in the lathe. 



I have already mentioned that I fused into a globule a specimen 

 of iridium obtained by me from the insoluble residuum of platinum 

 ore by Wohler's process. From this globule, while congealing, a 

 portion ran out from the inside, leaving a cavity and covering one 

 of its sides externally with an incrustation, among which crystalline 

 spangles, or facets, were discernible. The specific gravity of the 

 globule of iridium, from the specimen furnished by Messrs. John- 

 son and Cock, was taken by Mr. T. R. Eckfelt of the United States 

 mint at Philadelphia, and by Dr. Boye, both having balances of the 

 greatest accuracy, and being very skilful in the employment of 

 them. In the first instance there was a perfect coincidence in the 

 results obtained, 21*83 being the numbers found by both of these 

 gentlemen. Agreeably to another trial made by Dr. Boye, using 

 river-water instead of distilled, the number was 21*78, water being 

 in either case about sixty-eight, with allowance for the diflference of 

 the water, and the temperature being above the standard of 60°. 

 The specific gravity of the specimen may then be estimated at 21*80. 



The specific gravity of fused platinum, purified according to the 

 instructions of Berzelius, before subjection to the hammer, proved 

 in one specimen to be not more than 19*70, although by hammering 

 it became equal to 21*23. It is with fused platinum that fused 

 iridium should be compared. Of course the specific gravity of the 

 last-mentioned metal, when both are obtained by fusion, may be 

 assumed to be one-tenth greater than that of the former. Moreover, 

 as this metal is the only impurity existing in the standard platinum 

 of London, of Paris, or of St. Petersburg, it follows that a high 

 specific gravity is not to be viewed as a proof of purity. Accord- 

 ingly a specimen of platinum, purified from iridium by the Ber- 

 zelian process, and which had proved eminently susceptible of being 

 beaten into leaf, was found only to be of the gravity of 21*16, while 

 that of a specimen of standard Russian platinum, very briUiantly 

 white but inferior in malleability, presented to me by his Excellency 

 Count Cancrine, as a specimen of the purest platinum of the Russian 

 mint, was 21*31. 



Of rhodium I have fused two specimens, one of five pennyweights, 

 purchased of Messrs. Johnson and Cock, the other received through 



