Prof. T. Carnelley on the Periodic Lai 



9 



Relation 9. (a) For members of the third, fourth, fifth, sixth, 

 and seventh groups, and for even members of the second group, 

 the differences between the melting-points, and also between the 

 boiling-points of the chlorides, or bromides, or iodides of the odd 

 and also of the even members of each group diminish as we pass 

 from the chlorides to the bromides and thence to the iodides, and 

 (b) increase as the difference between the atomic weights of the two 

 positive elements increases. With even members of the first 

 group, exactly the reverse is the case. 



To exhibit this relation we may use the arsenic group, as 

 represented in the following Table : — 



Table VI. — Illustrating Relation 9. 



I. 



Difference 

 of atomic 

 weights of 

 elements 

 in I. 



Chlorides. 



Bromides. 



Iodides. 



% ft 



3 



U=i o 



•s ft 

 pq 



.B.B 

 ±2 ° 



3 •" 



a o 



■s ft 



PQ 



3 d 

 S 'o 

 © ft 



•8 ft 



pq 



As-P 



44 



47 

 91 or 89* 

 88 or 90* 



135 



179 



44 

 101 

 145 

 158 

 259 

 303 



54 



91 



145 



207 

 298 

 352 



43 



68 

 111 

 117 



185 



228 



49 



56 

 105 

 200 

 256 

 305 



91? 



19 

 110 

 116 

 135 

 226 



102? 

 -16 

 118 

 171 



187 

 289 



Sb-As ..... 

 Sb-P 



Bi-Sb 



Bi-As 



Bi-P 





* IfSb = 120. 



Relation 10. (a) The differences between the melting-points 

 or boiling-points of the chlorides, or bromides, or iodides of the 

 elements of Groups III. to vii., and those of the seventh or 

 halogen group increase algebraically from the chlorides to the 

 bromides and thence to the iodides. 



(b) With even members of the first and second groups these 

 differences diminish from chlorides to iodides. (See Table 

 VII.) 



Relation 11. The differences referred to under Relation 10 

 for Groups ill. to vn. increase as the algebraic difference 

 between the atomic weights of the positive elements increases. 

 (See Table VII.) 



For members of the first and second groups no rule can be 

 laid down. 



Relation 12. The above differences {Relation 10) between 

 the boiling-points are algebraically greater than those between 

 the corresponding melting-points. (See Table VII.) 



The above twelve Relations (together with a few others of 

 less importance) can at present be applied in no less than 

 3248 cases. Of these, 180 (or about 5 per cent.) are excep- 



