Prof. T. Oarnelley on the Periodic Law. 

 Table I A. (continued). 





Melting- 

 point. 



Boiling- 

 point. 



Authority. 



BaBr 2 



1085 

 1045 

 981 

 901 

 707 

 874 

 724 

 700 

 800 

 981 

 971 

 535 

 667 

 719 

 814 

 844 

 677 

 561 

 517 

 514 

 904 



"953 



972 



"576 



592 

 622 



Oarnelley. 



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NaCl 



NaBr 



Nal 



Cu,Cl., 



0u 2 I a 



AgCl 



AffBr 



Agl 



MgCl 2 



MgBr 



ZnCl 2 



ZnBr, 



Znl, ". 



CdCl 2 



CdBr 



Cdl 



HgCL 



HffBrl 



Hgl 2 .. 



CsOl 





to this rule occur either at the maxima or at the minima (i. e. 

 at the turning-points) of Meyer's curve of the elements {Mod. 

 Theor. der Chem.), or, in other words, with the tetrad elements 

 C, Si, Ti, &c, or the positive monad elements Rh, Ag y and Cs. 

 And further, the odd tetrad elements, when they are exceptions, 

 always have a lower melting-point or boiling-point, whilst 

 the even tetrad elements have a higher melting- or boiling-point 

 than would be required by the rule. These instances, there- 

 fore, must be looked upon, not as exceptional, but rather as 

 confirming the truth of the Periodic Law ; for they themselves 

 occur regularly and periodically. 



The above facts are illustrated by Table II., which exhibits 

 the values for the chlorides, bromides, and iodides of the 

 elements from Li to Ti. In the first column the elements 

 are arranged according to the size of their atomic weights ; 

 in the second, third, and fourth columns are given the melting- 

 points, boiling-points, and heats of formation of the chlorides, 

 and in the following columns those of the corresponding 

 bromides and iodides. 



This relation is rendered still more evident by the curve 

 shown in the diagram (Plate I.), in which the melting-points of 

 the halogen compounds are represented by the ordinates, and 

 the atomic weights of the positive elements by the abscissae. 



Relation 2. In passing from the first and second members 



