426 Wells and Walden — Double Chlorides, 



caesium in our analyses, because the salts of this type were 

 crystallized from solutions containing a large excess of caesium 

 halide. In order to convince ourselves that there was no mis- 

 take about the 4: 1 formulae we have prepared the two chlo- 

 rides according to the directions of von Hauer who described 

 them. The salts were extremely well crystallized and it was 

 easy to obtain them in a very pure condition. The results of 

 the analyses were as follows : 



Calculated for 

 Found. K 4 CdCl 6 . 



Potassium 32 '35 32 49 



Cadmium 23*39 23*36 2327 



Chlorine 44-00 44-12 44*24 



Calculated for 

 Found. (NH 4 ) 4 CdCl 6 . 



Ammonium 18*20 18-12 



Cadmium 27-91 27*87 28'22 



Chlorine 53*50 53.66 



These results confirm von Hauer's formulae, and the curious 

 fact must be accepted that caesium forms 3 : 1 double halides 

 with cadmium, while pgtassium and ammonium form salts of 

 the 4 : 1 type. 



The four types of cadmium double halides now known form 

 a very simple and symmetrical series, the ratios of the alkali- 

 metal to cadmium being 4: 1, 3 : 1, 2 : 1 and 1:1. The first 

 two of these types do not conform to Remsen's so-called law* 

 concerning the composition of double halides. 



Preparation and General Properties. — The compounds to 

 be described were prepared by making warm solutions of the 

 component halides, and after concentrating if necessary, cool- 

 ing to crystallization. Water, slightly acidified with the cor- 

 responding acid to prevent the formation of basic compounds, 

 was used as the solvent, and in one instance, where a solution 

 became syrupy from a large excess of a cadmium salt, alcohol 

 was also tried, but without any advantage. The conditions 

 were varied gradually in each case all the way from the point 

 where the solution was saturated with the caesium halide to 

 the point where it was saturated with the cadmium halide, 

 and so many experiments were made that we believe that no 

 double salt, capable of existence at the temperatures used, 

 was overlooked. It was noticed that variations in the concen- 

 tration of any given solution had little effect upon the identity 

 of the salt produced. In this respect the cadmium compounds 

 differ considerably from those of mercury, for with the latter, 



* Am. Chem. Jour., xi, 291. 



