98 PLATINA. 



All the metals are considered as simple bodies, 

 none having been decomposed or resolved into 

 other principles ; also, at one time, they were sup- 

 posed to be formed of a peculiar basis and an ima- 

 ginary inflammable principle called plilogisto7i. 

 This theory was very favourable to the idea of 

 forming metals, and transmuting or changing them 

 into each other. The existence of phlogiston is no 

 longer believed in, and the science of alchemy is 

 only remembered as affording an instance of the 

 dangers of false theories, and of the great credulity 

 of persons in many respects well informed. 



The oxide of a metal was formerly called a cal^r^ 

 and its conversion was supposed to be owing to the 

 loss of the phlogiston ; but it was observed that 

 the metal gained instead of losing weight by this 

 change ; in fact, it acquires just the weight of the 

 oxygen it combines with. When the oxides of me- 

 tals are made to part with their oxygen, hey are 

 reduced to the metallic state, and upon this 

 depends the art of reducing metals from their 

 ores. 



PLATINA. 



This metal was unknown in Europe before 1748, 

 and is still chiefly found in South America : it has 

 been also found in Estremedura, in Old Spain. 



In colour it is nearly as white as silver. It is 

 very difficult of fusion, and can only be melted by 

 the assistance of oxygen gas or by galvanic elec- 

 tricity. From its refractory quality, it is employed 

 for crucibles and other chemical utensils exposed 

 to heat, for which it is admirably adapted. 



It is also extremely ductile and malleable, and 

 may be drawn into very thin wire, and hammered 

 into thin plates. 



