W. Gibbs on the Platinum metals. 351 



quicblorid and blchlorid of ruthenium are invariablv present. 

 ^o ])artof the present investigation lias cost more labor than the 

 complete separation of iridium and ruthenium, the properties of 

 mixtures of the salts of these metals having sometimes almost 

 led to a conviction of the existence of new metallic elements in 

 the osmiridium. 



A perfect separation of ruthenium from iridium rnav be easily 

 effected by the following process which is applicable to all cases, 

 without reference to the state of oxydation iu which either metal 

 may exist. To the solution containing the two metals nitrite of 

 soda is to be added in excess, together with a sulhcient quantity 

 of carbonate of soda to keep the liquid neutral or alkidine. The 

 ^vhole is to be boiled until the solution assumes a clear orange- 

 yellow or orange color. If a green tint should be jterceptible 

 more nitrite of soda must be added and the solution again boiled. 

 I^oth ruthenium and iridium are converted into soluble double 

 nitrites. A solution of sulphid of sodium is then to be added in 

 small quantities at a time until a little of the precipitated sulphid 

 of ruthenium is dissolved in the excess of alkaline sulphid. The 

 ^I'st addition of the sulphid gives the characteristic crimson tint 

 due to the presence of ruthenium, but this quickly disappears 

 and gives place to a bright chocolate-colored precipitate. The 

 solution is then to be boiled for a few minutes, allowed to become 

 perfectly cold, and then dilute chlorhydric acid added cautiously 

 "»til the dissolved sulphid of ruthenium is f)recipitated and the 

 reaction is just perceptibly acid. The solution is then to be fil- 

 tered through a double tilter, and the sulphid of ruthenium 

 ^yashed continuously and thoroughly with boiling water. The 

 titrate is perfectly free from ruthenium: it is to be evaporated 

 ^^'ith chlorhydric acid and treated with sal-ammoniac in the man- 

 ner already "pointed out in speaking of the separation of iridium 

 ^'■^"^m platinum. The washed sulphid of ruthenium is to be 

 treated together with the filter with strong chlorhydric acid and 

 chlorid of ammonium added in quantity sufficient to form chlo- 

 ro-nnhenate of ammonium. Nitric acid is to be added from 

 ^'^e to time in small quantities until, with the aid of heat, the 

 }';iiole of the sulphid of ruthenium is oxydized nnd dissolved. 

 j'le liquid is then to be filtered, the filter well washed and the 

 ^''trate and washings evaporated to dryness on a water-bath, 

 ^^hen, after washing out the soluble salt with a strong solution of 

 ^ '^oi'id of ammonium the salt, KuCU,NH,Cl, remains almost 

 ^'"emieally pure. It is to be dissolved and converted into the 

 ??'^poundofchloridofmercurvandruthen-diamin, 2NH3KUCI + 

 %CI, by the process already described. From this salt chemi- 

 ^^'Lv pure ruthenium may be obtained by ignition, which is best 

 *^«ected in an atmosphere of hydrogen, as the reduced metal is 

 easily oxydized in the air. 



