boiling. 



clili)rhydric acid, giving a solution of chloro-iridate : the potash 



salt is decomposed with great difficulty. 



Plaiiaum.—Sohifiom of the alkaline nitrites exert a scarcely 

 sensible reducing action upon chlorplatinate of potassium or am- 

 monium, even after long boiling. The salt retains its color and 

 "■ changed from the solution on cooling. Whea 



other metals belonging to the same group are present, and the 



after add 



quantity of platinum is dissolved, giving a yellow salt very sol- 

 uble in water and alcohol. When nitrite of potash is added to 



" ' ■■ ■ immediately throws 



um: the same effect 

 _j produced in a solution of the yellow'salt above mentioned. 



Palladium.— A solution of either protochlorid or bichlorid of 

 palladium immediately becomes yellow or orange-yellow, when 

 an excess of nitrite of potash is added to it. Two different 

 double nitrites of palladium and potassium are usually formed 

 in this reaction. Both are soluble and are precipitated in a crys- 

 talline form by alcohol from concentrated .solutions. One of these 

 salts has a deep orange-red color, the other is lemon-yellow; both 

 are readily soluble in water, and alkaline sulphids precipitate 

 palladium completely from the solutions. 



These two salts were first described by Fischer.* 



Iihodmm.—^Y hen nitrite of potash is added to a solution con- 

 taining the sesquichlorid of rhodium no change is at first pro- 

 duced, but on heating the solution becomes yellow, and on 

 boiling or evaporation to dryness, part of the rhodium is precip- 

 itated in the form of a bright yellow or orange-yellow crystalline 

 powder which is extremely insoluble in hot or cold water, but 

 which dissolves readily in hot chlorhydric acid. Another por- 

 tion of the rhodium usually remains in the form of a yellow salt 

 soluble in water but insoluble in alcohol. The solutions of these 

 two salts are decomposed with great difficulty by boiling with 

 strong acids : alkaline sulphids give a dark brown precipitate ot 

 sulphid of rhodium soluble in a large excess of the precipitant 

 and completely precipitated from the solutions by the addition 

 of an excess of chlorhydric acid. Nitrite of soda also gives a 

 soluble and an insoluble salt with solutions of rhodium, but only 

 the soluble salt is formed when the rhodium solution is boiled 

 for a .short time with an excess of the alkaline nitrite. 



The application of these facts to the separation of the several 

 metals of the group is as follows : 



_ Platimim from iridiam.—HhQ separation of platinum fro"l 

 indium for the purpose of obtaining the two metals in a state oi 



