CHEMISTRY — BASKERVIIXE. 141 



Two important points require consideration, namely, the affinity 

 of thorium for oxygen and for nitrogen, and the high melting-point 

 of thorium. 



The illumino-thermit methods of Goldschmidt were tried with 

 many variations. Thorium oxide, mixed with aluminum powder in 

 calculated proportions and ignited with ignition mixture, is reduced, 

 to be sure, but the reaction takes place at a comparatively low 

 heat. The oxide is not completely reduced and the mass does not 

 completely melt. Numerous efforts were then made to prepare alloys 

 of thorium which, according to a general law, should melt at lower 

 temperatures than pure thorium. 



The use of zinc, lead, copper, and other metals or their oxides gave 

 negative results. The reaction was so violent at times as to proceed 

 with a pyrotechuical display and even dangerous explosions. Efforts 

 were made to reduce the oxide and form an alloy by means of a large 

 excess of aluminum in the powdered condition. An intimate mixture 

 was made in crucibles lined with magnesium oxide and protected from 

 the air by making a cement cover of magnesium oxide and chloride. 

 These crucibles were subjected to the heat of a powerful boiler fur- 

 nace for eight hours. While no satisfactory yield of metallic thorium 

 or alloy of thorium and aluminum was had in this manner, an alloy 

 of thorium, aluminum, and copper was obtained. 



Another interesting point is to be noted here, namely, that the small 

 amount of copper which occurs in ordinary aluminum is concentrated 

 by the thorium. This may in part be removed by repeated digestion 

 in ammonia, hydrogen dioxide, then electrolysis in oxalic solution. 



Without enumerating many other efforts to obtain the metal, it will 

 suffice to state that eventually we prepared the double potassium-tho- 

 rium fluoride in an anhydrous condition and reduced it by means of 

 finely divided aluminum which was free from copper. This was done 

 in a crucible lined with magnesium oxide and protected from the air 

 by a magnesia cover. Sufficiently high temperature was obtained by 

 burying the crucible in a mass of kryptol, which was heated by the 

 passage of a powerful electric current of 80 amperes and 220 volts. 

 In order to heat the mixture evenly a copper wire was wound around 

 the inner crucible several times in the form of a spiral. The heat 

 could be readily controlled. In this manner a regulus of thorium and 

 aluminum alloy was obtained containing a minimum amount of sil- 

 icon. When the thorium and potassium fluorides were mixed in the 

 proportion of 1 : 3 the regulus showed no crystalline structure under 

 the microscope. When the proportion was 1 : 2 the mass was a nest 

 of long crystals belonging to the hexagonal system. The aluminum 



