October 23, 1908] 



SCIENCE 



549 



taken up in a general course in inorganic 

 chemistry. 



In considering briefly the reasons why 

 it would seem best to remove at least a 

 number of these elements from the con- 

 fines of my definition I shall in general 

 limit myself to the presentation of certain 

 facts and figures gathered from the record 

 of the last half-decade. 



Hillebrand in discussing the analysis of 

 silicate and carbonate rocks mentions Ti, 

 Zr, V, Li, Ta, Cb, Be, Th, Ce, and the rare 

 earths as possible ingredients of the sili- 

 cate rocks, and adds in regard to Th, Ce 

 and the rare earths that "they are prob- 

 ably more common as constituents of sili- 

 cate rocks than has generally been sup- 

 posed; and A. A. Noyes and his associates 

 in their new system of qualitative analy- 

 sis have included Tl, Pt, Au, Se, Te, Mo, 

 Be, U, V, Ti and Zr. 



For convenience the periodic grouping 

 will be followed in the consideration of 

 the elements which we wish to discuss. 



In group (1) rubidium and csesium 

 clearly come under our definition, and 

 possibly also lithium. Lithium, as already 

 stated, is an ingredient to be reckoned 

 with in rock analysis, while its importance 

 in water analysis is shown by its presence 

 in over forty samples of water from dif- 

 ferent parts of the world in amounts vary- 

 ing from traces to one per cent. In 

 Clarke's data of geo-chemistry, from which 

 these figures were taken, we find rubidium 

 mentioned as present in about twenty 

 samples of water, CEesium being more 

 rare. 



The last report of the United States 

 Mineral Kesources shows an output of 

 about 2,200 short tons of lithium minerals 

 since 1903 with a value of about $40,000. 



During the past five years the greater 

 part of the work upon these elements has 

 been concerned with the formation of new 

 compounds. It is perhaps of interest to 



note in this connection that iron alums of 

 selenic acid containing csesium and rubi- 

 dium have been prepared, while the corres- 

 ponding ammonium and potassium salts 

 have not been successfully produced. 



In group (2) we have the elements 

 beryllium and radium. Concerning the 

 former, I need add no word after the 

 masterly paper upon " The Vagaries of 

 Beryllium, ' '^ given before this body a year 

 ago by Chas. L. Parsons. To the student 

 of pure chemistry, if not as yet to the 

 technical chemist, the element offers most 

 interesting problems. May we not hope 

 that a more extended study of the produc- 

 tion and properties of this metal of low 

 specific gravity will make possible some im- 

 portant application in the arts. 



It is not the purpose of this paper to 

 take up the subject of radium and radio- 

 activity more than to mention the stimu- 

 lus which this branch of work has given to 

 the study of uranium and thorium min- 

 erals and of their natural associates. 



In group (3) we find yttrium and cer- 

 tain members of the cerium group. These 

 bring us to the consideration of the rare 

 earth group, comprising within its ever- 

 growing boundaries about sixteen names 

 which seem at times to be almost the des- 

 pair of the chemical housekeeper who may 

 wish to file away each element in its ap- 

 propriate group-cupboard of the periodic 

 system. 



Notable among the aids to the worker in 

 this field during the past few years have 

 been the publication of Bohm's "Dar- 

 stellung der Seltenen Brden," Leipzig, 

 1905, in two volumes of about 500 pages 

 each. Schilling's "Vorkommen der Sel- 

 tenen Erden," Munich, 1904, and Meyer's 

 "Bibliographic der Seltenen Erden," 

 Hamburg, 1905. Among the voluminous 

 papers describing excellent work in this 



= Science, N. S., Vol. XXVI., No. 670, pp. 569- 

 74, November 1, 1907. 



