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BELL SYSTEM TECIIXICAL JOURNAL 



(luring the discliarge — not ionized atoms of a gas sustaining the dis- 

 charge, as pre\iously — and tlrawn to and through the cathode by the 

 entire voltage across the tube. The anode of the tube must be made in 

 a special manner; in Aston's experiments it consists of a "paste" 

 made of graphite, of lithium iotlide, of a halogen salt of the metal to 

 be analyzed, and sometimes of other salts as well. Ions of the other 

 elements in the paste and from the gas in the discharge mingle with 

 the desired ions in the pencil which shoots through the cathode per- 

 foration, l)Ut this is no iiunnNcnience. (juitc the reverse, as the traces 



Additiondl elemenli: 55 Cs, one liolope at i33 



eoHg. isotopes at 202,201. and m the iMnge 197-200 



Fig. 10 — The First Si.x Rows of the Periodic Table of the Elements, Showing the 



Atomic Masses of the Isotopes of the Elements which Have Been .-Knalyzed. 



The Data Come from Aston's Tabulations 



which they leave on the olate are con\enicnt points de replre for 

 fixing the exact location o^he traces left by the ions being analyzed. 

 In this manner the elements scandium, titanium, vanadium, chromium, 

 manganese, cobalt, copper, gallium, germanium, strontium, yttrium, 

 silver and indium were studied — thirteen altogether, bringing up to 

 forty-seven the number of elements which ha\e been anahzed in the 

 fourteen years since neon was first disco\ered to ho iiuiltii)le. 



All of these forty-seven elements except two lie in ilie lirsi Ine 

 periods of the periodic table, and they ha\'e been written out in the 

 tabular form in Fig. 10. The symbol of each element is preceded 

 by its atomic number, and below the symbol lies not the combining 

 weight of the element as in the tables one usualh' sees hanging on the 

 walls f)f chemical lecture-rooms, but the ensemble of the atomic 

 weights of its various kintls of atoms — the atomic masses of its isotopes, 

 as the term is. Where no number or set of numbers is given, the 

 analysis has not yet been made. Of the first fifty-five elements of 



