PAPERS OX CHEMISTRY AND PHYSICS 225 



molten metal of its dissolved oxygen. Misch metal has 

 properties which make it quite desirable for this pur- 

 pose : melting point 750"C, beat of oxidation 1740 calor- 

 ies per gram, and alloys with most metals are readily 

 formed. 



"With respect to the yttrinm gronp. considerably more 

 diffii2ulty is encountered in the isolation of the mixed 

 metal or any of its individual members. The metals are 

 less electropositive, it is true, but their melting points 

 are vei*^' much higher. Yttrium is reported as melting at 

 1250= C, Erbium 1250° C and ytterbium as high as 1800° 

 C, although there is some doubt with respect to the last 

 named. These high melting points are not the greatest 

 evil to be overcome. Most of the anhydrous chlorides of 

 the yttrium group have low melting points as compared 

 with those of the cerium group. Yttrium chloride melts 

 at 6S0' C, dysprosium chloride at 700^ C, and ytterbium 

 chloride at 880° C. Thus in the electrolysis of the fused 

 chlorides of this group it is impossible to obtain the metal 

 in the fused state, and since the temperature of the bath 

 must be maintained in the neighborhood of 1000° C there 

 is a large loss of salt due to volatilization. It has been 

 found that ^i:trium chloride is quite volatile slightly 

 above its melting point. 



Since the metals of the yttrium group are less electro- 

 positive than the cerium group and are also slightly less 

 positive than aluminium, it has been possible to prepare 

 the mixed metals of this group by a solution of the oxides 

 in a molten bath of cryolite and subjecting them to elec- 

 trolysis similar to that of the production of aluminum.- 

 It is also possible to use the double fluorides of the 

 yttrium group instead of the cryolite. By these methods 

 there is very little loss of any material due to volatiliza- 

 tion. 



It is quite probable that most of the rare earth metals 

 as individuals will not command a great commercial use 

 since the isolation of their salts is a veiw difficult matter. 



Hicks. Loc. cit. 



