318 Wells — Complex Chlorides containing Gold. 



them by cooling hot solutions and others by evaporation 

 to crystallization on the steam-bath. 



The method of analysis for silver, gold and chlorine 

 was the same as that described for Pollard's salt in the 

 previous article. 3 The cesium was determined by weigh- 

 ing the chloride after removing the other metals and evap- 

 orating to dryness. 



Cesium- Zinc- Auric Chloride, Cs 4 ZnAu 2 Cl 12 . — This salt 

 gave somewhat larger crystals than the other members of 

 the series. The crystals were prismatic in habit, and 

 sometimes as much as 3 or 4 mm. in length. Some of the 

 crops were yellow in color, but other products showed a 

 reddish or even a dark red color^ and the red crops fre- 

 quently showed variations in the individual crystals from 

 yellow through various shades of red. There was no 

 appreciable difference in the composition of the yellow 

 and red products. It appeared that solutions which gave 

 red crops when rather dilute gave yellow ones upon con- 

 centration by evaporation. The cause of the changes in 

 color is not definitely known, but it is suspected that the 

 red color was caused by a slight contamination, due to the 

 reducing action of filter-paper, with the very strongly col- 

 ored salt Cs 4 Au' 2 Au'" 2 Cl 12 , which has been found to give 

 strong color-effects with the mercuric triple salt, as will 

 be explained further on in this article. 



It was found that this zinc salt can be prepared in the 

 presence of a considerable excess of zinc chloride, as well 

 as of cesium chloride. This is due to the fact that the 

 double chlorides Cs 3 ZnCl 5 and Cs 2 ZnCl 4 , described 4 in this 

 laboratory long ago, are so readily soluble as not to inter- 

 fere. 



The salt is decomposed by cold water with the precipi- 

 tation of CsAuCl 4 , but the latter dissolves in the presence 

 of sufficient water. 



The following analyses of separate crops under varying 

 conditions were made : 



I II III IV V Calculated for 



Yellow Yellow Eeddish Red Red Cs 4 ZnAu 2 Cl 12 



Cs .... .... .... .... 37.51 



Zn 5.23 4.83 4.72 5.82 4.84 4.61 



Au 27.46 27.68 27.48 27.80 27.88 27.84 



CI .... .... .... .... 30.04 



3 Loc. eit. 



4 Wells and Campbell, This Journal, 46, 431, 1893. 



