Obtaining Iridium and Osmium from the Platinum residue. 371 



The rotating armature, has excited a great deal of curiosity here. 

 The -mechanics were very much puzzled by it and supposed it went 

 by steam. 1 took care to conceal the battery which excited it and 

 conveyed the galvanic fluid along two slender wires, without attract- 

 ing their attention. 



1 send you the above little instrument, the peculiarity of it is, that 

 it makes its own magnet while revolving. 



Art. XIII. — A Method of obtaining Iridium and Osmium from the 

 Platinum residue; by F. Wohler. Translated by J. C. Booth, 

 received in a letter to the editor, dated Berlin, April 20th, 1834. 



The black powdery residue, which remains upon treating the 

 platinum-sand with nitro-muriatic acid, contains, as is well known, 

 a certain quantity of a natural alloy, osmjum-iridium and probably no 

 inconsiderable proportion of uncombined iridium in powder. It has 

 always been a difficult matter to separate the two last metals from 

 the ore, as well in consequence of the difficult decomposition of the 

 alloy, as on account of the presence of large quantities of foreign 

 ingredients, and particularly of titanate of iron. The discovery of 

 a simple and unexpensive method of decomposition was so much the 

 more desirable, since this remainder has accumulated in places where 

 platinum is largely worked, and it is not improbable that an easy 

 method of obtaining iridium, a metal nearly allied to platinum, may 

 lead to a highly useful mode of application in the arts. It was for 

 this purpose necessary to find the means of extracting osmium and 

 iridium alone without affecting the titanate of iron ; for since the par- 

 ticles of the latter cannot be separated by the magnet or otherwise 

 mechanically, the presence of such large quantities of iron and tita- 

 nic acid might render the employment of such a method difficult. 

 The method I am about to describe appears to me sufficiently adap- 

 ted to the purpose, and could be employed in the large way without 

 difficulty. It is founded on the means resorted to by Berzelius of 

 bringing iridium, insoluble in aqua-regia, to a soluble slate and one 

 suited for the preparation of its other combinations, — viz. by passing 

 chlorine over a heated mixture of iridium and chloride of sodium* 

 The process for the platinum-residue* is as follows : 



It is unnecessary to powder it. The trouble of mineralogists, will however be 

 amply repaid, by previously spreading it out upon paper and seeking out the larger 



Vol. XXVI.— No. 2. 48 



