W. Gibbs on the Platinum metals. 349 



fied by crystallization but usually retains traces of ruthenium. 

 The rose-red solution of the ruthenium salt contains a small 

 quantity of platinum from which it cannot be wholly freed by 

 the difference in solubility of the two salts. Chlorid of ammo- 

 nium may be employed in this process in place of chlorid of 

 potassium. 



To obtain a complete separation the following process may be 

 followed with advantage. The chloro-ruthenate of potassium, 

 separated as far as possible from the platinum salt, is to be heated 

 with a solution of nitrite of potash in quantity sufficient to con- 

 vert the whole of the ruthenium into the soluble yellow double 

 nitrite of ruthenium and. potassium, carbonate of potash being 

 added in small quantities so as to keep the solution neutral or 

 alkaline. The yellow or orange solution is to be evaporated to 

 dryness in a water bath, the dry mass reduced to powder and 

 boiled with absolute alcohol until the ruthenium salt is completely 

 dissolved. This is best effected in a flask furnished with a con- 

 densing tube bent upward so that the alcohol vapors may be 

 condensed and jflow back into the flask. The boiling need not 

 oe continued for a very long time as the ruthenium salt is readily 

 soluble in alcohol. The solution is then to be filtered off from 

 the undissolved salts and these are to be washed with absolute 

 alcohol until the washings are colorless, or until they no longer 

 give the characteristic ruthenium reaction with sulphid of am- 

 monium. The filtrate and washings may then be distilled to 

 separate and save the alcohol, water being first added in small 

 quantity. The residue in the retort or flask is then to be evapo- 

 rated with chlorhydric acid which readily decomposes the double 

 nitrite and yields a fine deep rose-red solution of the chloro-ru- 

 thenate of potassium, containing at most only a trace of platinum. 

 The mass of salts undissolved by the alcohol contains nearly all 

 t'^e platinum in the form of chlorplatinate of potassium which is 

 ^^i-'ily separated. The solution of chloro-ruthenate of potassium 

 ^s now so pure that it gives the reactions of a chemically pure 

 ^a|t. To obtain the ruthenium in a state of absolute purity the 

 aturated solution 



, - .^ V........ , -o aporated and the 



^^y mass washed with a little cold water to remove the alkaline 

 chloiids. The chloro-ruthenate of potassium is in this manner, 

 tof the most part at least, converted into chloro-ruthenate of am- 

 J^'ionium. This salt is then to be dissolved in hot water, a solu- 

 *j' n of ammonia added, and the liquid boiled until it assumes a 

 ^'-ar yellow or orange-yellow color, after which it is to be evapo- 

 rated to dryness upon a water-bath. In this manner ^the rutheni- 

 ^f is converted into the chlorid of ruthen-diamin, 2NH3,RuCl-f- 

 !^flO, discovered by Glaus. The yellow mass is to be dissolved 

 ^^ boiling water and a solution of chlorid of mercury added. A 



