266 



Mr. W. Crookes. 



[May 31, 



belongs to the group of earthy metals, consisting of aluminium, 

 beryllium, thorium, zirconium, cerium, lanthanum, didymium, and the 

 yttrium family, together with titanium, tantalum, and niobium. The 

 sought-for earth is insoluble in excess of potash ; this excludes 

 aluminium and beryllium. It is not precipitated by continued boiling 

 with sodic thio sulphate ; this excludes aluminium, thorium, and 

 zirconium. Fused with acid potassic sulphate, the resulting com- 

 pound is readily soluble in cold water ; this excludes tantalum and 

 niobium. Evaporating to dryness with hydrochloric acid and heating 

 for some time does not render the mass insoluble in water; this 

 excludes titanium and silicium. It is easily soluble in an excess of a 

 saturated solution of potassic sulphate ; this excludes thorium, the 

 cerium group, some of the numerous members of the yttrium group, 

 and zirconium. The only remaining elements among which this 

 elusive body would probably be found are those members of the 

 yttrium family which are not precipitated by potassic sulphate. 



The yttria earths form a somewhat numerous family. Fortunately 

 for chemists, a mineral rich in yttria earths — samarskite — has been 

 found lately in large quantity in Mitchell County, North Carolina, 

 and to this mineral I accordingly now directed my attention. 



The following list of elements of .the yttrium and its allied 

 families said to occur in samarskite and similar minerals may be con- 

 sidered complete to the present time. 



Name. 



Cerium 



Decipittm . ... 

 Didymium . . 

 Didymium p. 



Erbium 



Holmium. . . . 

 Lanthanum. . 

 Mosandrum . 

 Samarium. . . 

 Scandium . . . 

 Terbium 



Thulium 



Ytterbium . . . 



Yttrium 



Yttrium oc. . . 

 Yttrium f3. . . 



Absorption 

 spectrum. 



No 



Yes 



Yes 



Yes 



Yes 



Yes 



No 



No 



Yes 



No 



No 



Yes 



No 



No 



No 



Yes 



Hydrogen equiva- 

 lent of metal.* 

 (Type of oxide 



M 2 0.) 



47 



1 



57 



•o 



48 



•5 



47 



•o 



55 



•3 



54 



•o 



46 



•o 



51 



■2 



50 



•o 



14 



•7 



49 



•5 



56 



•5 



57 



•9 



29 



•7 



52 



■2 



49 



•7 



* As it is at present doubtful whether the oxides of several of the metals in this 

 table belong to the type M 2 0, M 2 3 , or MO, I have, for the sake of uniformity and 



