SILVER. 24 i) 



is a triple muriate of ammonia and platina. The precipitete is 

 then exposed to a strong heat, which expels the acid and alkali, but 

 leaves the platina in a pure state. Platina is thus obtained in the 

 form of a spongy mass, which is rendered more compact by 

 pressure while red hot. It is of a white colour, like silver ; it is 

 very malleable and ductile; its specific gravity is 21 '5. It is not 

 oxidized by exposure to air or moisture, and requires an intense 

 heat for its fusion. Next to iron, it is the hardest of the metals, 

 and like it admits of being welded. It is insoluble in all the acids, 

 except the nitro-muriatic, which dissolves it with facility. It 

 enters into combination with sulphur, phosphorus, and many of 

 the metals. The salts of platina are formed by digesting its oxide 

 in the acids with which it is to be combined. The most delicate 

 test for the detection of platina is the muriate of tin, which gives a 

 bright red colour to any of its solutions. 



Uses. — Metallic Platina, like gold, has no action on the human 

 body ; but it is stated by the French physicians that the medicinal 

 and poisonous properties of the salts of this metal are nearly allied 

 to those of the salts of gold, From its extreme hardness and 

 infusibility, platina is employed in making chemical apparatus, 

 particular crucibles, where these require to be exposed to intense 

 heat, or to the action of corrosive liquids ; and for coating steel, 

 copper, and various metallic substances, to protect them from the 

 atmosphere. It is also used in the construction of Professor 

 Daniell's pyrometer, the best instrument which has hitherto been 

 invented for measuring high temperatures, Davy's safety lamp, 

 Clarke's night light without flame, the wheels of watches, telescope 

 mirrors, and for a variety of other useful purposes. 



Genus III.— SILVER. 



Argent, Fr. ; Argento, It. ; Plata, Sp.; Silber, Ger.; Rupah, Hind. 



The ores of Silver are numerous ; it is sometimes found native 

 but more frequently mineralized with oxygen, sulphur, and with 

 the carbonic and muriatic acids. It occurs also combined with the 



