260 OXIDES. 







with the lead, and oxidizes its surface ; 

 but instead of becoming rusty, the 

 surface becomes dull, and of a darker 

 colour. 



Q. Why is it difficult to keep SILVER BRIGHT ? 



A. Because the vapour of the air 

 oxidizes its surface, and tarnishes it. 



Q. Why do silver TEA-POTS and SPOONS 

 tarnish more quickly than silver ore or bullion ? 



A. Because alloy (of some baser 

 metal) is used to make it more hard and 

 lasting ; and this alloy oxidizes more 

 quickly than silver itself. 



Q. Why does GERMAN silver turn a dingy 

 yellow in a few hours ? 



A. German silver has a great affinity 

 for oxygen, and shows its oxidation by 

 a sickly yellow tarnish, instead of rust. 



Q. If quicksilver (or mercury) is tarnished 

 like copper and lead, Why does it preserve its 



BRILLIANCY in BAROMETERS and THERMOMETERS ? 



A. Because air is excluded from it, 

 and no moisture comes in contact with 

 it to oxidize (or tarnish it). 



Q. Is GOLD affected by the atmosphere ? 



A. Not readily: gold will never 



