Wells and Dupee — Ccesium- Cupric Chlorides. 91 



Art. IX. — On the Caesium- Cupric Chlorides ; by H. L. 

 Wells and L. C. Dupee. 



As a continuation of the work done in this laboratory on 

 double halogen salts, we have taken up the ceesium-cupric 

 chlorides, which had never been thoroughly investigated. The 

 result has been the discovery of four double salts belonging to 

 three different types. The beauty of the crystals in size and 

 form, and the magnificent and unexpected colors of some of 

 them have made the investigation a very interesting one. The 

 colors of the anhydrous salts, yellow and red, were perhaps not 

 very remarkable since anhydrous cupric chloride is reddish 

 brown, but since water of crystallization is supposed to give green 

 and blue colors to cupric salts, we were considerably surprised 

 to find that a brown salt, Cs 3 Cu 2 Cl 7 . 2H 2 0, was hydrous. The 

 color of this hydrous salt is, however, not without analogy, 

 for a garnet-red, hydrous lithiumcupric chloride is known, 

 LiCuCl 3 . 2^H 2 according to Chassevant,* or LiCuCl 3 . 2II 2 

 according to Meyerhoffer ;f moreover Engel has described^: a 

 garnet-red compound HCuCl 3 . 3PI 2 0, and Sabatier's red salt 

 H 2 CuCl 4 . 5H 2 0,§ is similarly exceptional in color. 



In this connection, it should be noticed that cupric chloride, 

 when dissolved in water with an excess of caesium chloride 

 gives a bright yellow solution when it is hot and concentrated. 

 It is well known that solutions of cupric chloride in concen- 

 trated hydrochloric acid have the same yellow color. 



A list of the formulae of the salts to be described, with their 

 colors, is given below. The first salt has already been de- 

 scribed by Grodeffroy. I 



Cs 2 CuCl 4 Brilliant yellow. 



Cs 2 CuCl 4 . 2H 2 Bluish green. 



Cs 3 Cu 2 Cl 7 . 2H 2 Brown. 



CsCuCl 3 * Garnet-red. 



The previously described cupric double halides containing 

 alkali-metals and ammonium belong to two of the types which 

 we have found in investigating the CEesium-cupric chlorides. 

 A list of all those that we have been able to find is given 

 below. Four of the double fluorides have been recently 

 described by von Helmont.^f 



* Compt. Rend., cxiii, 646. f Monatshefte, xiii, 716. 



± Compt. Rend., cvi, 27M. § Compt. Rend., cvi, 1724. 



|| Berichte, viii, 9. TfZeitschr. Anorgan. Chera., iii, 115. 



