xvni THE CLASSIFICATION OF THE ELEMENTS 457 



It is not necessary to consider in detail the table which 

 Newlands used to illustrate the Law of Octaves. In spite 

 of the larger number of elements, the families were reduced 

 from ten to seven, in order to maintain the idea of octaves. 



The members of the triads, recurring at intervals of fourteen 

 elements, were separated by unrelated elements occupying 

 the intermediate octaves, thus disguising to some extent the 

 relations indicated so clearly in the first table. 



Mendeleeff on "periodicity" (1869). This fault was 

 remedied in a short note "On the Relationships of the 

 Properties to the Atomic Weights of the Elements," sub- 

 mitted to the Russian Chemical Society in March, 1869, by 

 D. Mendeleeff. In Mendeleeff s table the number of 

 families was increased to nineteen, and, in spite of many 

 gaps and a large number of interrogation-marks, all 

 Table C. MendeleefFs First Table of the Elements. 



H=i 



Be = 9,4 



C=I2 



0=i6 



Na = 23 



Si = 28 

 8-32 



Cu = 63,4 



" = 68' 



?= 7 o 



As = 75 



86=79,4 



Br = 8o 



Sr = 87^6 

 La = 94 

 Th = ii8? 



Zr= 90 

 Nb = 94 

 Mo= 96 

 Rh-r 104,4 

 Ru= 104,4 

 Pd=io6,6 

 Ag=io8 



Cd=II2 



Ur=ii6 

 Sn = n8 



Sb=I22 



Te=i28? 



J = I2 7 



Cs=i 33 

 Ba=i 3 7 



Ta=i82 

 W=i86 

 Pt= 197,4 

 Ir-i98 

 Os=i99 



Au=i97? 



