178 SILVER. 



LESSON 79. 



Silver and Mercury. 



Ful'minate, to explode with a loud report. 



Silver is a heavy, sonorous, brilliant, white metal, only 

 moderately hard, but exceedingly ductile, and of great mal- 

 leability and tenacity. It is found in various parts of the 

 world, particularly in Peru and Mexico, in a metallic state : 

 also in the state of an alloy, of a sulphuret, of a salt, and in 

 that of an oxyd. It is the most brilliant of metals, and 

 nothing surpasses it in splendour except highly polished steel. 

 It is chiefly used for ornamental work, for domestic utensils, 

 and for current coin : but for these purposes it is generally 

 alloyed with copper, without which it would not have suf- 

 ficient hardness to sustain much wear. You may know 

 when silver is pure by hreating it in a common fire, or in the 

 flame of a candle ; if it be alloyed, it will become tarnished ; 

 but if it be pure silver, it will remain perfectly white. Of 

 the salts of silver the nitrate is best known, and when melted 

 and run in moulds, it forms the lunar caustic of the apothe- 

 cary. A solution of it mixed with a little gum water, forms, in 

 conjunction with an alkali, the indelible ink, used in marking 

 linen. 



Silvering may be performed on the same substances, and 

 by similar methods with gilding. But as works of this kind 

 are liable to tarnish, they are seldom used. Plating with 

 silver is performed in the following manner : one of the sur- 

 faces of an ingot of copper is rendered smooth and clean, 

 and is sprinkled over with a saturated solution of borax ; 

 upon this is laid a plate of fine silver, about one twelfth the 

 weight of the copper, and the two are carefully bound to- 

 gether by wire. The mass is now exposed to a full red heat, 

 and the silver adheres to the copper. The ingot is then 

 passed through a rolling-press, and formed into a plate; 

 both the silver and copper extending uniformly during the 

 whole process, at the conclusion of which, the two metals 

 are inseparably united. 



Mercury or quicksilver has been known from the earliest 

 ages of the world. In the temperature of our atmosphere, 

 it is a white fluid metal, having the appearance and brilliancy 



