136 MANGANESE — LEAD. 



of a "beautiful golden yellow color, and is employed 

 for various ornamental purposes in the arts, under 

 the name of mosaic gold. 



309. Manganese, like tin, is found only as an 

 oxide ; it is a metal in many respects considerably 

 resembling iron, but having a much stronger attrac- 

 tion for oxygen, and consequently obtained in the 

 metallic state with very great difficulty ; it forms 

 several oxides, only one of which, however, is a base; 

 some of its salts are employed in dyeing ; and the 

 peroxide is much used in the process for obtaining 

 chlorine (191). Manganese is very often found asso- 

 ciated with iron in rocks and stones, and not unfre- 

 quently exists in minute quantity in soils; it is com- 

 paratively speaking, however, a rare metal. 



310. Lead is obtained almost exclusively from the 

 native sulphuret; it never is found in the pure me- 

 tallic state. The sulphuret is roasted, by which the 

 sulphur is gradually driven oif, and an impure oxide 

 formed, which remains mixed with a large quantity 

 of sulphuret ; this is then smelted with small coal or 

 other carbonaceous matter. Lead has a strong affinity 

 for oxygen, in consequence of which it tarnishes 

 slowly at common temperatures, and quickly when 

 melted. At a red heat, lead is gradually converted 

 into a yellow substance called litharge — this is an 

 impure protoxide ; if still longer exposed to the air 

 and heat, it absorbs more -oxygen and becomes red 

 lead or minium ; besides these two, there is yet a 

 third oxide of lead, which, however, cannot be formed 



