EARTHS'. 295 



5. POLARITY. Electro-positive, as appears from the original ex- 

 periment of Sir H. Davy, in which it was attracted to an iron wire 

 connected with the negative pole of the galvanic series. 



Remark. That alumina so extensively diffused and so familiarly 

 known, should contain a metal, distinct and remarkable in its pro- 

 perties, and with the aid of potassium, so easily obtained, is a very 

 interesting confirmation of the views of the illustrious Davy,* and must 

 give celebrity to that of Dr. Wohler. 



Should the basis of the most important of the earths, namely, si- 

 licium, which Prof. Berzelius has, by the aid of the same agent, 

 potassium, now placed fully within our reach, eventually prove, after 

 fusion, to be truly metallic, it would be an interesting addition to the 

 series ; but in any event, the great fact that the earths are all oxides, 

 is sufficiently established. 



SEC. VII. ZIRCONIA. 



1. NATURAL HISTORY AND DISCOVERY. 



Never found pure in nature; discovered first in 1789, by Klap-< 

 roth, in the jargon or zircon, a precious stone from Ceylon, in which 

 he found 37.5 silica, .5 nickel and iron, and 68. of the new earth, 

 which from its parent mineral, he called zirconia. In 1795, found 

 by him in the hyacinths of Ceylon, and in 1796, discovered by Mor- 

 veau, in those from the brook of Expailly, in France ; Vauquelin 

 confirmed the discovery by farther experiments, f 



2. PROCESS. 



(a.) To the pulverized zircon, add three or four times its weight, J 

 of caustic potash, and fuse it in a silver crucible, throwing in the mix- 

 ture, spoonful by spoonful, and waiting for the fusion of each portion 

 before another is added t and after all are fused, increase the heat and 

 maintain it for an hour and a half. Wash the contents of the cru- 

 cible abundantly in boiling hot water, to remove the alkali. Now 

 add muriatic acid to dissolve the zirconia, some silica is taken up by 

 the acid, which is precipitated by heating the fluid, and removed by 

 filtration. Lastly, add potassa ; the zirconia precipitates ; or it may 

 be thrown down by carbonate of soda, and must then be washed 

 sufficiently with pure water. 



* Whose premature death, the friends of science and mankind will long deplore. 



t Dr. Thomson, of Glasgow, has discovered 18 per cent, of zirconia, in the Silli- 

 manite, a new prismatic mineral species fpund at Chester, in Saybrook, Conn, and 

 first analyzed, named, and described by the late Prof. Bowen, who found it to consist 

 of alumina, 54.11, silica, 42.66, iron, 1.99, and water .51. Dr. Thomson found a sim- 

 ilar constitution, except that he discovered the zirconia as above stated. Am. Jour. 

 Vol. VIII, 195. 217; Vol. XII, 159, and Vol. XVI, 207. 



t Five or six times, Four. II, 210 nine times, Ure's Pict. 815. 



