268 INDIUM AND THALLIUM IN 



Within the limits of the present contribution it is impossible 

 to enter into a full discussion of the practical results here 

 described ; that must be reserved for subsequent publication 

 elsewhere. Some general conclusions drawn from a detailed 

 comparison of the various salts which have been examined is 

 given, however, in the summary which follows. 



SUMMARY 



1. The ditetragonal bipyramidal series, consisting of the salts (a) K,T1C1, 2H,0, 

 (6) (NH),T1C1, 2H a O, (c) KJnCl. 2H,0, (d) Rb.TlBr, 2H a O, () K.In 

 Br, 2H,0, was investigated, and full crystallographical details are given 

 for all the salts except K 3 InBr, 2H,0, which effloresces so readily that 

 exact measurements are impossible. It had formerly been considered 



were isomorphous. The investigation has shown that all the salts of 

 this isomorphous series have two molecules of water of crystallisation. 



2. The rhombic bipyramidal series, consisting of the salts (a) Rb s TlCl 6 H,0, (6) 



Cs.TlCl, H,0, (c) (NH 4 )JnCl s H ,O, (d) RbJnCl, H ,0, () Cs.InCl, H,0, 

 (/) (NH 4 ) a InBr 6 H,0, (g) Rb,InBr 5 H,0, (h) Cs,InBr 6 H 2 0, was investi- 

 gated. Of these, the indium salts with the possible exception of 

 (NH 4 ),IuCl, H a O were prepared for the first time, and quantitative 

 analyses are appended. The series is isomorphous, and crystallo- 

 graphical details are given in full, except in the case of (NH 4 ) a InBr s H a O, 

 which is very deliquescent. 



3. The following salts were found to crystallise in cubes in the regular 



system : KTlBr, 2H a O, (NH 4 )TlBr 4 2H,0, RbTlBr, H,0, andCsTlBr,. 

 Of these the first two had formerly been taken as rhombic. 



Details of the crystallography of the salt K,Tl a Br, 3H a O, which 

 crystallises in the ditetragonal bipyramidal class, are also appended. 



4. The results of the investigation on the isomorphous relationships in the 



above-mentioned series, and the additional salts K a FeCl 5 H a O and 

 (NH 4 ),FeCl t HjO (which are isomorphous with the second series), may 

 be summarised as follows : 



(a) Crystal Habit 



The alkalies stand in the following order : NH 4 , Rb, Cs. Cl and 

 Br are very closely related. The salts of Fe, In, Tl differ widely from 

 each other. 



