372 Obtaining Iridium and Osmium from the Platinum residue. 
It is mingled with an equal weight of previously dried and pow- 
dered chloride of sodium and introduced into a tube of green glass 
of sufficient length and width. (In the large way, tubes of earthen 
ware could be used.) ‘This is laid in a tube furnace (and that em- 
ployed by Liebeg, in organic analysis seems best adapted to the pur- 
pose ;) one end of the large tube is attached to the chloride of cal- 
cium tube, to dry the chlorine which passes throughout the appara- 
tus, while from the other end proceeds a balloon to retain the subli- 
ming osmic acid. From the opposite end of the balloon, passes a 
small bent tube into dilute ammonia in order to catch the last por- 
tions of the same volatile acid. Ignited charcoal is then laid under 
the whole length of the tube, so that the mixture occupying two 
thirds of the interior diameter, is gently ignited. Chlorine is now 
slowly evolved and passed through the apparatus. It is at first so 
fully and in such quantity absorbed, that no bubbles pass through 
the ammonia. When this occurs, which is the case after the lapse 
of a couple of hours by employing one hundred grm. the operation 
is completed, the apparatus suffered to cool and taken apart. 
The explanation of the operation is, that the soluble chlorides of 
iridium, and sodium, and of osmium and sodium, are formed and ti- 
tanate of iron remains undecomposed, Through moisture in the chlo- 
rine, chloride of osmium seem to be constantly decomposed in such 
a manner that hydrochloric and osmic acids are formed and osmium 
precipitated, to. be anew subjected to the action of chlorine. A 
small quantity of deep green or red chloride of osmium is generally 
found in the farther part of the tube. This much is certain, that 
the greater part of the osmium is obtained as osmic acid. ‘The sep- 
aration of the two metals is likewise founded upon the experiments 
of Berzelius.* 
particles of osmium-iridium, since they are even by the above treatment only super- 
ficially acted on and might otherwise be lost. It farther deserves attention, that 
there must be among these particles some insoluble in aqua-regia, an alloy of gold 
probably with osmium or iridium. At least in one of my experiments, according to 
the above method, I obtained no inconsiderable quantity of gold. In succeeding 
trials, with new portions of the remainder, I could not detect the slightest traces of 
this metal; whence the conclusion that in the first portion particles were present, 
probably a rarely occuring alloy of gold with another metal. It is lastly to be re- 
marked that silver is contained in the platinum-remainder. For in that which I em- 
ployed (from America) I found no inconsiderable quantity of chloride of silver, 
which was extracted by ammonia,—an operation which the remainder must under- 
go to obtain the silver. 
* Poggendorf’s Annalen, XIII. 467, XV. 208. 
