MERCURY. 103 



resembling in appearance a vegetation, and called 

 arbor Diance. 



Silver is not soluble in the hydro-chloric acid 

 (muriatic acid), yet, when this acid is added to a 

 solution of nitrate of silver, it unites to the oxide, 

 and a white curdy precipitate falls down, which 

 is the muriate of silver, or, in conformity with the 

 new nomenclature, the chloride of silver. If this 

 precipitate be fused by a gentle heat, a semi-trans- 

 parent mass is formed, called formerly luna cornea* 

 or horn silver, the fused muriate of silver. 



Silver is also dissolved by the sulphuric acid, and 

 the sulphate of silver is used as a chemical test. 

 Silver also unites to sulphur and phosphorus. 



Silver, when employed for coin is alloyed with 

 copper to increase its hardness. Our coin con- 

 tains thirty-seven parts silver and three parts 

 copper. 



MERCURY. 



This metal, called also quicksilver, is always fluid 

 when in the usual temperature of the atmosphere ; 

 but when exposed to an intense degree of cold, it 

 is frozen into a solid mass, and is then malleable. 

 The temperature necessary for this purpose is 39. 

 The cold is sometimes so great within the polar 

 circle as to freeze the mercury in the thermometer ; 

 but in this country that can only be effected by 

 exposing it to a freezing mixture. 



Mercury also boils at 655, and then evaporates, 

 and may be distilled from one vessel to another. 



It is sometimes found in nature in a pure state, 

 but usually it is united to sulphur, with which it 



H 4 



