316 Wells — Complex Chlorides containing Gold. 



shows interesting cases of isomorphous replacement 

 between two univalent atoms and one atom that is 

 bivalent. 



The very intense black colors of the two salts contain- 

 ing univalent silver and aurous atoms is very remarkable. 

 They form precipitates as black as precipitated lead sul- 

 phide, while the crystals of the aurous salt sometimes 

 show a coppery luster similar to that often displayed by 

 solid dyestuffs. 



An attempt was made to prepare a cesium-calcium- 

 auric chloride, but no such compound was found under a 

 wide range of conditions. There is little doubt, however, 

 that other bivalent metals besides those that have been 

 used in the present investigation would yield triple chlor- 

 ides with cesium and auric gold. 



In preparing these triple chlorides by crystallization a 

 large excess of cesium chloride, over the theoretical quan- 

 tity, is usually desirable, but the solutions should gener- 

 ally be very dilute in respect to gold in order to avoid the 

 deposition of the sparingly soluble double salt CsAuCl 4 . 

 Although some of the compounds have been obtained from 

 practically neutral solutions, the presence of much hydro- 

 chloric acid, even up to the full strength of the concen- 

 trated liquid, is favorable to their formation, apparently 

 by making them more stable and less soluble. In several 

 instances, where a solution deposited a triple salt mixed 

 with CsAuCl 4 , it was only necessary to dilute considerably 

 with concentrated hydrochloric acid in order to obtain a 

 pure crop of the triple salt after dissolving the mixture by 

 heating and then cooling. 



It is characteristic of these triple salts, and also of Pol- 

 lard's ammonium compound, that they form very minute 

 crystals, usually less than 1 or 2 mm. in diameter, whether 

 they are formed by the slow cooling of the solutions or by 

 evaporation on the steam-bath. The crystals of the dou- 

 ble salt CsAuCl 4 that are frequently deposited with them 

 are invariably of far greater size. The triple salts are 

 evidently very sparingly soluble in their cold mother- 

 liquors, for the latter usually show by their pale yellow 

 colors that very little gold is left in solution in the usual, 

 preferable cases where the gold is subordinate to the 

 other constituents in its proportion. 



All of the analyzed products were shown to be evidently 



