92 Wells and Dupee — C(esium- Cupric Chlorides. 



2 : 1 Type. 1 : 1 Type. 



(NH 4 )„CuCI 4 . 2H„0 NH 4 CuCl, . 2H o 



K„Cu0l 4 .2H„O NH 4 CuF, . 2*H",0 



K 2 0uF 4 KCuF s 



(NH 4 ) o CiiF 4 .2H o RbCuF 3 



LiCuCl 3 . 2H 2 



It is to be noticed that this list contains salts which corre- 

 spond exactly to three of the caesium compounds, and that the 

 group of 2 : 1 salts with two molecules of water is a conspicu- 

 ous one. 



The salt Cs 3 Cu 2 Cl 7 . 2H 2 is an interesting one because it is 

 apparently the only known double halide of an alkali metal 

 with a bivalent metal, which has the 3 : 2 ratio. 



The caesium salts were investigated systematically by start- 

 ing with a solution of 50 g. of caesium chloride and adding to 

 this from 3 to 5 g. of cupric chloride at a time, evaporating 

 after each addition and observing the products. At the same 

 time another series of experiments was made by beginning 

 with a solution of 50 g. of cupric chloride, adding caesium 

 chloride to this gradually and operating in the same manner 

 as in the other case. Many additional experiments were made, 

 sometimes with the use of as much as 200 g, of caesium chlo- 

 ride, and a number of crystallizations were made in the pres- 

 ence of hydrochloric acid of various strengths. It is believed 

 that no double salt capable of existence either in warm solu- 

 tions or at ordinary temperatures has been overlooked. 



The salts were so well crystallized and so distinct in form 

 and color that there was no difficulty in selecting pure products 

 for analysis. The usual precautions, often mentioned in com- 

 munications from this laboratory, were taken for the removal 

 of mother-liquor from the crystals. 



In analyzing the salts copper and caesium were determined 

 in one portion, the first as subsulphide, the other as normal 

 sulphate. The chlorine was determined in separate portions, 

 by the usual gravimetric method. 



Anhydrous 2 : 1 Cazsium- Cupric Chloride, CsJJuCl^: — This 

 salt, which Godeffroy first described, forms magnificent, yel- 

 low, orthorhombic prisms, which were often obtained sev- 

 eral centimeters in length and several millimeters in thick- 

 ness. The crystals are usually attached at one end, and 

 they often arrange themselves in parallel position, forming- 

 flat clusters. Doubly terminated, short crystals were occa- 

 sionally observed. Its formation was observed, with 50 g. 

 of caesium chloride, in the presence of from 5 to about 25 g. 

 of cupric chloride. It can be recrystallized from water if the 

 solution is made so concentrated that crystals form on cooling, 



