844 W. Gihhs on the Platinum metals. 



Osmium. — A solution ol 

 nitrite of potash to osrniou 

 forming the well known beautiful red salt discovered by Freraj. 

 The solution may be evaporated to dryness without decomposi- 

 tion. The nitrite may therefore be added with great advantage 

 when solutions containing free osmic acid nre to be evaporated, 

 or even transferred from one vessel to another. No other re- 

 ducing agent yet applied answers the same purpose, as the 

 osmium is obtained at once in a very convenient form for preser- 

 vation. When a solution of osmic acid, to which nitrite of pot- 

 ash has been added, is evaporated sufladently and then allowed 

 to cool, beautiful garnet red octahedral crystals of the osmite of 

 potash separate. These should be dried in pleno, over sulphuric 

 acid, and not in contact with paper or organic matter, which 

 partly reduces the osmious acid to the brown sesquioxyd of os- 

 mium. Nitrite of potash exerts no sensible action when boiled 

 with a solution of chloro-osmate of potassium. Any salt which 

 may be formed is very soluble in water. 



IiiUhenium.—\Yher\ a solution of nitrite of potash is added in 

 excess to the sesquichlorid of ruthenium, either free or in com- 

 bination with chlorid of potassium or ammonium, a yellow or 

 orange-yellow color is produced, but no precipitate is formed. 

 A preciselv similar change occurs when the ruthenium is in the 

 form of bichlorid, but in this case the change of color is produced 

 more slowly, andi usually requires heating or even boiling. The 

 change of color produced is in both cases owing to the formation 

 of an orange-yellow double salt of ruthenium and potassium 

 which is very soluble in water and alcohol ; its relations to alco- 

 hol in particular enable us to distinguish ruthenium from the 

 other platinum metals more perfectlv than has hitherto been 

 possible. Nitrite of soda forms. a similar salt with solutions ot 

 the bichlorid of ruthenium. 



When a few drops of sulphid of ammonium are added to a 

 solution of the ruthenium double salt above mentioned, a mag- 

 nificent crimson color is produced. This reaction furnishes a 

 characteristic test for ruthenium of the greatest value, since it is 

 not, like Claus's beautiful reactions with sulphocyanid of potas- 

 sium or sulphuretted hvdrogen, materially afi'ected by the pres- 

 ence of the other metals of the same group. The test may oe 

 most advantageous] V applied as follows: The liquid supposed to 

 contain ruthenium is first to be rendered neutral or alkaline by 

 addition of carbonate of soda or potash. I prefer to use an ex 

 cess of alkali. Nitrite of potash in solution is then to be addeo, 

 the liquid boiled for an instant, allowed to be become perfectly 

 cold and a drop or two of colorless sulphid of ammonium addea. 

 On shaking, the color appears and rapidly deepens to the tjnesi 

 red. When the quantity of ruthenium present is very smali, ^ 

 when large quantities of the other platinum metals are ais« 



