BY A. LEIBIUS, PH. D. 213 



through Deville and Debray, since it forms a fusible alloy with 

 platinum, which, when it contains 25 30 \o of Iridium, resists 

 every acid. Vessels of such an alloy are already manufactured by 

 Desmontis in Paris, and whilst the technical application of 

 Iridium, which hitherto has been but very limited, has thus been 

 brought into a new phase, the Russian Government has given 

 especial instructions with regard to the development of their 

 vast resources of platinum ores, from which not only the valuable 

 platinum, but also the no longer valueless Iridium are obtained. 



Although the Australian Gold does not contain anything 

 like a sufficient quantity of Iridium to become one of the resources 

 for obtaining the latter for technical purposes, I thought that 

 the importance which this interesting metal seems destined to 

 have, would sufficiently warrant my drawing your attention to 

 the same by giving you this short outline, and exhibiting a few 

 specimens of the metals and its compounds, as well as its usual 

 companion, the metal Osmium, of which I shall speak presently. 



With regard to the different compounds into which Iridium 

 is capable of entering, I need not trouble you. The solutions of 

 the different salts represent, as already mentioned, almost all the 

 colours of the rainbow, but unfortunately they do not keep long, 

 but decompose under change of colour. 



The most important Iridium Salt, namely the Irid-Salmiak ; 

 already mentioned, I have here. This dissolves in 20 parts of 

 water, but colours distinctly yellow even 40,000 parts. 



On heating it to red heat, pure Iridium remains behind. 



OSMIOI. 



I will now shortly describe the companion of the Iridium the 

 Osmium. It is very difficult to get Iridium quite free from 

 Osmium, of which traces adhere with great pertinacity. The 

 operation for preparing Osmium out of Osmiridium falls in Tvith 

 the preparation of Iridium by chlorine gas, as before described. 



The Osmium which is collected during the preparation of Iri- 

 dium, partly as osmic acid, in a balloon attached to the tube in 

 which the mixture of Osmiridium and Salt was heated, and partly 

 as Chloride and Bichloride of Osmium, is dissolved in dilute 



