Displacement in their own Mother -liquor 209 



holds whether we take the triads in column or in line. Com- 

 paring salts in the same line, we see that replacing Rb by Cs 

 causes a rise of specific gravity which is twice as great as that 

 caused by the substitution of Rb for K. Comparing salts in 

 the same column, the replacement of Cl by Br causes more 

 than double the rise caused by the substitution of I for Br. 

 However we regard it, we see that the specific gravity of the 

 salts is a periodic function of their molecular weight, within 

 the ennead. 



TABLE IV. The Salt in Crystal 



K Rb Cs 



(a) Values of T (C) 



23-4 22-9 23-1 Cl 



23-4 23-0 21-4 Br 



24-3 24-3 22-8 I 



(6) Values of D 



1-951 2-706 3-982 Cl 



2-679 3-210 4-455 Br 



3-043 3-428 4-508 I 



.MK 



(c) \ alucs of 



D 



38-233 44-71 .j J-3IO Cl 



44-460 51-553 47-820 Br 



54-580 61-986 57-670 I 



(d) Values of \" 1 ' 



loJJ 



2-124 2-489 2-350 Cl 



2-470 2-864 2-657 Br 



3-032 3-444 3-204 I 



In the third compartment (c) we have the values of or 



the displacement of one molecule (MR) of salt stated in gramme- 

 of water, and in compartment (d) the same constant is stated 



in gram-molecules of water -gg ) . In dealing with the specific 



gravities, we saw that, whether we follow the columns or the 



lini -, they increase with im HM^<- d nmlrriil.ir weight. In tin- 

 case of the molecular di>j>l;ic rnn-nt^ this holds tm the columns 

 but not for the lines. In these the salts of rubidium have tin- 

 greatest molerul.ir displacement, tin potassium salN h.i\e the 

 d the eju-xiuin .dt-> occupy an interim di.ite pn<itii.n. 



B. III. I I 



