648 MERCURY. 



humid way. It is dissolved in small quantity by concentrated 

 sulphuric acid, but precipitated from that solution by water. 



Sulphotantalic acid, TaS 3 , is prepared with most advantage 

 by exposing tantalic acid to a bright red heat in a porcelain tube, 

 and passing bisulphuret of carbon over it. It forms a grey 

 pulverulent matter, having much the appearance of plumbago. 

 It is a good conductor of electricity. 



Chloride of tantalum, TaCl 3 , obtained on heating tantalum 

 in pure chlorine gas, is, in the state of vapour, a yellow gas re- 

 sembling chlorine, which condenses into a white floury powder, 

 having a shade of yellow, and in no way crystalline. 



Tantalic acid dissolves in alkalies and forms salts, but they 

 are not crystallizable and are decomposed by all other acids 

 even by carbonic acid. 



ORDER VIII. 



METALS OF WHICH THE OXIDES ARE REDUCED TO THE METALLIC 

 STATE BY HEAT (NOBLE METALS.) 



SECTION I. 



MERCURY. 



Eq. 1265.8 or 101.43 ; Hg (hydrargyrum.} 



Mercury or quicksilver, as it is named from its fluidity, has 

 been known from all antiquity. The most valuable European 

 mines of this metal are those of Idria in Illyria, and Almaden in 

 Spain. It is found, to a small extent, in the metallic state. Its 

 principal ore is a sulphuret, native cinnabar, from which the 

 metal is obtained by distillation with lime or iron. The quick- 

 silver of commerce is in general a highly pure substance. 

 When contaminated with other metals, its fluidity is remarkably 

 impaired. Mercury may be purified by distilling it from half 

 its weight of iron turnings, or by digesting the metal with a 

 small quantity of nitric acid, or with a solution of chloride of 

 mercury, which rids it of the metals more oxidable than itself. 



Mercury is liquid at the usual temperature, its colour is white 

 with a shade of blue when compared with silver, and it has a 



