EARTHS. 297 



(A.) Zirconia differs from silica, in being much more soluble in 

 acids, and in being insoluble in alkalies, but it is soluble in alkaline 

 carbonates ; in this last property it differs from alumina and glucina. 



('.) There is a great resemblance between oxide of titanium and 

 zirconia, in most of their properties ; but tincture of galls precipi- 

 tates oxide of titanium reddish brown zirconia in yellow flocks.* 



4. POLARITY. From analogy, supposed to be electro-positive; 

 and to be attracted to the negative pole of the galvanic series. 



5. COMBINING WEIGHT, 48, consisting of zirconium, 1 proportion, 

 40, and oxygen, 1 proportion, 8. Thomson. It has been supposed 

 from some experiments of Berzelius, that it is 30 or 33. 



ZIRCONIUM. 



1. HISTORY AND PROCESS. 



Sir H. Davy discovered, that when zirconia is ignited with po- 

 tassium, the latter is oxidized, and dark metallic particles are diffused 

 through the alkali. 



Berzelius has more recently procured this base, as he did sili- 

 cium ; that is, by heating with a spirit lamp, in a tube of glass or iron, 

 a mixture of potassium and hydro-fluate of zirconia and potassa, care- 

 fully dried ; at a temperature below ignition, the earth is reduced to 

 the metallic state, and without any luminous appearance ; the mass is 

 next washed with boiling water, and then digested for some time in 

 pure muriatic acid ; the residue is pure zirconium, f 



2. PROPERTIES. 



(a.) Black as charcoal; it is a powder. 



(6.) Not oxidized by boiling water, or sulphuric or muriatic acid, 

 but dissolved by aqua regia, and hydro-fluoric acid, the latter evolv- 

 ing hydrogen. 



(c.) Zirconium burns intensely in the open air, with a slight in- 

 crease of heat, but far below luminousness, and produces zirconia. 



(d.) It combines with sulphur, forming a chesnut brown sulphuret, 

 insoluble in muriatic acid, and alkalies ; but which burns brilliantly, 

 regenerating the earth, and evolving sulphurous acid.J 



(e.) Does not conduct electricity ; it is capable of being pressed 

 out into scales of a dark gray color, having somewhat of the metal- 

 lic appearance, but it is not perfectly settled whether it ought to be 

 called a metal. 



3. COMBINING WEIGHT not accurately determined. See zirco- 

 nia, 5. 



* Ann. of Philos. XIII, 83. Turner, and Eng. Quar. Jour. XV111, 157. 



t Ann. of Philos. N. S. VIII, 123. 



38 



