SPECIFIC GRAVITY AND DISPLACEMENT OF SOME SALINE SOLUTIONS. 137 



Replacing Br by I in KBr, RbBr, or CsBr produces increases in the displacements 

 which become greater as the atomic weight of the metal increases. 



There is a greater increase produced by replacing K by Rb in KI than that 

 produced when Rb takes the place of K in KBr ; a similar effect is seen with the 

 corresponding salts of rubidium and caesium, but in both instances the replacing of one 

 metal by another causes a smaller change than when iodine takes the place of bromine 

 in the bromide of the metal. The exchange of iodine for bromine produces increases in 

 the values of v which rise with the increase of the atomic weight of the metal in 

 combination ; as was previously observed, the replacement of chlorine by bromine 

 caused changes in the increase of v which diminished with the increase in the atomic 

 weight of the metal. We may summarise the foregoing observations by saying that 

 the replacement of the acid in a salt of the general formula MR (where M = K, Rb, 

 or Cs, and R = CI, Br, or I) by another acid causes a greater change in the value of the 

 displacement of a solution containing 1/16 grm.-raol. of the salt in 1000 grams of 

 water at 19 '5° C. than the replacement of the metal by another metal. The only 

 exceptions to this are when Cs takes the place of Rb in RbCl, and when Br replaces 

 CI in CsCl, this latter being the smallest change produced when one acid is replaced by 

 another. The values of the differences of the displacements for 1/16 grm.-mol. 

 solutions of the salts of the halides are given in the table below. 





K. 



Diff. 



Rb. 



Diff. 



Cs. 



Diir. 

 (K by Cs). 



CI 



Diff. 



Br 



Diff. 



I 

 Diff CI by I 



0-469 



0-336 



0-436 



0-455 



0-398 



0-791 



0-619 



0-303 



0-747 



0-417 



0-802 



0-720 



1-088 



0-431 



1-183 



0-472 



1-200 



0-903 















In the table, differences on the same line are, inter se, comparable ; the differences in 

 the same column headed " Diff." are also comparable. 



§ 59. The salts of the oxy halides will now be dealt with in a manner similar to that 

 of the halides. 



K. Diff. Rb. Diff. Cs. 



C103 



BrO, 



2-785 + 0-398 = 3-183 + 0-486 = 3-669 

 2-761 + 0-296 = 3-057 + 0-454 = 3-511 



Diff. - 24 



0-126 



-0-158 



If, in a solution containing 1/16 grm.-mol. KCIO3 per 1000 grams of water at 



19*5° C, we replace the chlorine by bromine, the process is accompanied by a decrease 



in the displacement of the solution by an amount equal to — 0-024 Gi ; if the operation 

 TKANS. ROY. SOC. EDIN., VOL. XLIX., PART I. (NO. 1). 18 



