474 



PRINCIPLES OF CHEMISTRY 



Dift Diff. Difl. Ditf. 



Mg=12j 8 *=31J 44 0-81 8 



Li 7) Ca =20v Ae = 75\ S =16, 



16 3*8 44 3x8 



Na*23 8r =44 Bb = 119 Se-40 



16 13x8 12x44 18x8 



K =39' Ba =68) A Bi=207) Te = 64) 



and pointed dut some really striking relationships, such as the following: 

 F o!9. 



Cl = 86-5 =19 + 1^*6 

 Br=80 =19 + 2x16-5 + 28. 

 I = 127 = 2 x.19 + 2 x l6'5 -f 2 x 28. 



A. Strecker, in his work Theorien und Experimente zur Bestimmung 

 der Atomgewichte der Elemente ' (Braunschweig, 1859), after summarising 

 the data relating to the subject, and pointing out the remarkable series of 

 equivalents 



Cr,-26-2 Mn-27-6 Fe~28 Ni = 29 Co80 Cu=31-7 



remarks that: It is hardly probable that all the above-mentioned relations 

 between the atomic weights (or equivalents) of chemically analogous elements 

 are merely accidental. We must, however, leave to the future tbe discovery 

 of the law of the relations which appears in these figures.' l 



In such attempts at arrangement and in such views are to be recognised 

 the real forerunners of the periodic law ; the ground was prepared for it 

 between I860 and 1870, and that it was not expressed in a determinate form 

 before the end of the decade may, I suppose, be ascribed to the fact that only 

 analogous elements had been compared. The idea of seeking for a relation 

 between the atomic weights of all the elements was foreign to the ideas then 

 current, so that neither the vis tellurique of Be Chancourtois, nor the law of 

 octaves of Newlands, could secure anybody's attention. And yet both De 

 Chancourtois and Newlands like Dumas 'and Strecker, more than Lenssen 

 and Pettenkofer, had made an approach to the periodic law and had dis- 

 covered its germs. The solution of the problem advanced but slowly, because 

 the facts, but not the law, stood foremost in all attempts*, and the law could 

 not awaken a general interest so long as elements, having no apparent con- 

 nection with each other, were included in the same octave, as for example : 



1st octave of 



Newlands . . 



7th Ditto 



Pd 

 Te 



Au 



Pt&Ir 

 Os or Th 



Analogies of the above order seemed quite accidental, and the more so as 

 the octave contained occasionally ten elements instead of eight, and when two 



1 * Ea ist wohl kanm anztmehmen, dass alle ii Vorhergehfcnden hervorgehobenen 

 Beziehangen zwischen den Atomgewichten (oder Aequi valenten) in chemischen Verh51t 

 nissen einander ahnJjche Elemente bloss zufallig sind. T)ie Auffindung der in dieseo 

 Zablen gesetzlichen Beziehungen mttssen wir jedoch dex Zqkunft iiberlassen.' 



