158 JoUK]N"AL OF THE MiTCHELL SoCIETY [Marcll 



of fine balances. There is little demand for it at present in jewelry 

 except in the case of fine crystals of pure color. At one time it was 

 supposed to be peculiarly appropriate and was much used in mourn- 

 ing jewelry. Artificial zircons have been more or less successfully 

 produced. 



The brilliancy of the liffht given off by zirconia 



OXY-HYDROGEN . •■ & & 



LIGHT ill the oxy-hydrogen flame was first observed by 



Hare in- 1820 in his effort to fuse it. After the 

 development of the Drummond or lime light it was suggested that 

 zirconia be used as a substitute for the lime, offering the advantages 

 of slight absorbing power for carbon dioxide or water. In 1868 du 

 Motay used it in one of the lamps lighting the Tuileries. l^apoleon 

 III was so pleased with the result that he ordered its installation in 

 all of the lamps illuminating the court and gardens. The zirconia 

 light attracted much attention on the part of inventors and others. 

 On account of the purity of the light and the high emissive power of 

 the zirconia it was recommended for scientific use, as in polariscopes, 

 spectroscopes, etc., but this more especially refers to the next form. 



With the introduction of the Welsbach mantles 



GAS MANTLES 



interest in the Drummond light diminished. The 

 first incandescent mantles made by Welsbach in 1880 consisted essen- 

 tially of zirconia. Later this was largely substituted by the oxides 

 of thorium and cerium which have a higher emissive power. Zirconia 

 is used in admixture with these and other rare earths. 



A number of attempts have been made to use 



INCANDESCENT • i ,- i- n^ • • 



LiGHj metallic zirconium m the form oi filaments m in- 



candescent electric lamps. Its electrical conduc- 

 tivity and high fusing point should render it quite suitable for this 

 purpose. Korolkow has made an examination of the electrical resist- 

 ance, emissive power, and expansion coefficient of zirconium filaments, 

 but such determinations are considerably affected by the presence of 

 even small amounts of impurities. One difiiculty which has to be met 

 is the preparation of pure zirconium on a commercial scale and at a 

 reasonable cost. Most of the experiments with zirconium filaments 

 have been carried out with the more or less impure metal, sometimes 

 associated with the carbide which itself has been said to be unsuitable 



