780 



SCIENCE. 



[N. S. Vol. XVII. No. 437. 



mentions it in his 'Principles of Chemis- 

 try,' that Chroiistsehoff made the an- 

 nouncement before the Russian Chemical 

 Society, but had published no complete in- 

 vestigation. Two years ago, Brauner, 

 working along one line, and I, on another, 

 independently announced the complexity 

 of that element. 



It is generally accepted now from the 

 published work that the property of emit- 

 ting rays which affect the photographic 

 plate is not a specific property of thorium, 

 but characteristic of a constant contaminat- 

 ing constituent of that element. It is well 

 known also that, while some of these radia- 

 tions or emanations affect the photographic 

 plate, some do not. The electrical method 

 of measurement (quantitative) has been 

 substituted in our work and improved 

 methods of fractionation are being used, 

 whereby we seem to be approaching a non- 

 radio-active thorium and one possessing 

 that property in high degree. Further, 

 similar compounds of thorium fractions 

 similarly treated show almost no differ- 

 ence with the Rowland grating referred to, 

 yet show marked divergence in their radio- 

 active properties. The radio-active work 

 is being done by Mr. G. B. Pegram, of the 

 Department of Physics in Columbia Uni- 

 versity. 



I have not come from 'away down 

 south' to the center of commercial activity 

 of all the Americas to tell you how these 

 rare substances are to be had at low cost, 

 advertise their uses, form a combination 

 and arrange for their sale at a good profit, 

 although one of my neighbors ranks high 

 among Knickerbocker mergers. The fourth 

 period in rare earth activity is coexistent 

 with the extension of the use of some of 

 them for illuminating purposes. The price 

 of thorium nitrate fifteen years ago was 

 over five hundred dollars per pound. Now 

 the market price is about five dollars per 



pound. Conunerce required thorium com- 

 pounds; they were provided. Commerce 

 demanded thorium compounds at a rea- 

 sonable price ; the demands were met. The 

 prices of certain of the impure rare earths 

 occurring in nature with thorium are high, 

 but their values do not follow weU-known 

 economic laws and are purely fictitious. 

 When uses are found, the prices of these 

 by-products will fit the demand. 



In this maze of an enticing problem one 

 imagines much and many speculate more. 

 Not unfrequently, especially of late, have 

 we been treated with irenic disquisitions as 

 to the location of these rare elements in the 

 natural system. It appears to be forgotten 

 that Mendeleeff used his table to correct 

 the formulas of the typical oxides of cer- 

 tain elements, as, for example, lanthanum 

 (LaO to LaaOa). The fact is forgotten 

 that the atomic weights, now ascribed, 

 would be materially different were the 

 type different. The ascribed atomic 

 weights are dependent upon the synthesis 

 or analysis of the sulphates almost without 

 exception. It is forgotten that '-yl' salts, 

 like uranyl, chromyl sulphates are possible 

 for these elements, as recently shown by 

 Blandel for titanium and Matignon for 

 praseodidymium and neodidymium. Fur- 

 thermore, it is forgotten that the sulphate 

 method is absolutely defective, as Schiitzen- 

 berger pointed out. This has been verified 

 by Wyrouboff, Dennis, Brauner and 

 Pavlicek, and Demargay, as well as myself. 

 Therefore, all attempts to arrange these 

 elements, some of which are known to. be 

 complex, in the periodic table are veriest 

 speculation, which can profit little. It is 

 quite as true also that the table should re- 

 ceive no discredit because it fails to ac- 

 count for them with our present knowl- 

 edge. According to its author the table 

 reserves twenty-three places for their oc- 

 cupancy. 



