BY A. LEIBIUS, PH. D. 211 



over Irid.), causes the same to sink to the bottom of the melting 

 pot, where it is easily separated from the Gold. It is through this 

 process that the Sydney Mint has collected, in its crude state, 

 the Osmiridium, which, since its establishment, has amounted to 

 about 3 Ibs. 



There are several methods for extracting pure Osmium and 

 pare Iridium out of this impure Osmiridium. The method 

 adopted by me was the one given by Woehler, and which, for 

 working on a small scale, at all events, is the most convenient. 

 I will shortly describe it : 



The quantity of Osmiridium taken under operation was 8 

 ounces, which were powdered in a steel mortar, and mixed with 

 an equal quantity of fused Salt (Na. CL), the mixture introduced 

 into a glass tube, such as used for analyses, and heated in a gas 

 furnace, whilst moist chlorine gas was allowed to pass slowly for 

 about 3 hours over the mixture, heated to a dull red heat. By 

 this means a double salt of Chloride of Sodium with Chloride of 

 Iridium is formed, as well as a double salt of Chloride of Sodium 

 with Chloride of Osmium. But a great part of the Chloride of 

 Osmium formed is again decomposed by the water of the moist 

 chlorine gas into osmic acid, (which escapes, and is collected in a 

 balloon which is in connection with the glass tube) and into 

 metallic Osmium and Hydrochloric Acid. But the metallic 

 Osmium gets again formed into Chloride of Osmium, and com- 

 bines to a double salt, 2 Aeq. Os C1 2 + 4 HO = Os O , Os, 4 HC1. 

 The contents of the glass tube, which at the end of the operation 

 contain the double Chlorides of Iridium and Osmium with 

 Sodium, are dissolved in water which leaves titaniferous Iron 

 and other impurities of the Osmiridium undissolved, whilst the 

 double chlorides just mentioned are readily soluble. But only 

 about 30 lo of the w r eight of Osmiridium employed are brought 

 in solution by this process. A repetition of the same with the 

 dried residue extracts a little more, so that after three operations I 

 got about 50 lo in solution. 



This solution, which is dark red-brown, is distilled with 

 strong nitric acid in a glass retort, to convert the Chloride of 

 Osmium into Osmic Acid, which distills over and collects in 

 dilute Ammonia, The residue in the retort is poured, whilst still 



