320 Wells — Complex Chlorides containing Gold. 



C esium-Cupric- Auric Chloride, Cs 4 CuAu 2 Cl 12 . — Start- 

 ing with the beautiful garnet-red double salt CsCuCl 3 , a 

 large sample of which has been preserved in this labora- 

 tory since its preparation by L. C. Dupee, 5 experiments 

 were made at first with cupric chloride and with auric 

 chloride in excess in various proportions, but the triple 

 salt did not appear until a rather large excess of cesium 

 chloride was used. In such solutions, when they are cold, 

 it forms a pale brown precipitate upon the addition of 

 concentrated hydrochloric acid, but the minute crystals 

 that form upon cooling hot solutions are very black, 

 although their streak is pale brown. 



Four distinct crops prepared by cooling were analyzed. 

 The first two were made from rather concentrated, 

 slightly acid solutions the first of which contained much 

 more copper than the second and gave somewhat variable 

 results, while the others were obtained from the same 

 solutions after dilution with about equal volumes of con- 

 centrated hydrochloric acid : 



Calculated for 



I II III IV Cs 4 CuAu 2 Cl 12 



Cs :...-.. 37.20a 37.40a 37-.55 



Cu 4.16 3.88 4.68 4.92 4.49 



Au 26.89 29.91 27.94 27.66 27.88 



CI 30.18 30.02 30.08 



a By difference. 



In making the analyses the gold was precipitated by 

 means of ammonium oxalate in the presence of a little 

 free oxalic acid, and the copper was precipitated in the 

 filtrate with hydrogen sulphide and weighed as Cu 2 S. 

 After boiling off the H 2 S the chlorine was determined by 

 the usual gravimetric method. 



Cesium-Mercuric- Auric Chloride, Cs 4 HgAu 2 Cl 12 . — It is 

 easy to prepare this salt in a pure condition by cooling 

 strong hydrochloric acid solutions that are very dilute in 

 respect to auric chloride and especially to mercuric chlor- 

 ide, but which contain a considerable excess over the theo- 

 retical amount of cesium chloride. It is preferable also 

 to have a very little nitric acid present in order to avoid 

 the reduction of auric chloride to the aurous condition by 

 the action of filter-paper or dust. 



5 Wells and Dupee, This Journal, 47, 91, 1894. 



