476 Wells — Alleged Variable Composition of 



Art. XLI. — The Alleged Variable Composition of 

 Triple Chlorides Containing Silver and Gold; by 

 Horace L. Wells. 



[Contribution from the Sheffield Chemical Laboratory of Yale University.] 



A few months ago I made 1 a re-investigation of 

 Pollard's ammonium-silver-auric chloride 2 and showed 

 that this salt has the formula (NH 4 ) 6 Ag 2 Au 3 Cl 17 instead 

 of the slightly differing one, (NH 4 ) 8 Ag 3 Au 4 Cl 23 , ascribed 

 to it by Pollard. There was no indication, however, from 

 the results of either of us, that this compound has a 

 variable composition. Soon afterwards I described 3 the 

 salt Cs 2 AgAuCl 6 as one of five analogous triple chlorides, 

 the others of which contained zinc, mercury, copper, and 

 aurous gold in place of the silver of the first one (Cs 4 Zn- 

 Au 2 Cl 12 etc.), these compounds, also, were undoubtedly 

 of constant composition when free from isomorphous and 

 other impurities. 



It is much to be regretted that when these salts were 

 described I was unaware that Professor Emich and his 

 associates, of Graz, Austria, had previously published 

 results of investigations upon triple halides containing 

 silver and gold. Emich published 4 a preliminary commu- 

 nication upon a new microchemical reaction for gold, 

 silver and rubidium (and cesium), based upon the 

 formation of magnificent blood-red crystals when solu- 

 tions of the three chlorides (in the case of rubidium) are 

 evaporated upon the microscopic object-glass. These 

 tests are evidently very excellent and useful ones. 



My thanks are due to Professor Emich for a very 

 courteous letter, together with reprints of the articles 

 published by himself and his associates, calling my 

 attention to their priority in work with triple halides 

 containing silver and gold. This priority is, of course, 

 acknowledged, but it may be observed that only one salt, 

 the one to which I have ascribed the formula Cs 2 AgAuCl 6 , 

 has been analyzed both by me and by them, and that they 



1 This Journal, 3, 257, 1922. 



2 Jour. Chem. Soc, 117, 99, 1920. 

 8 This Journal, 3, 315, 1922. . 



* Monatsh. f . Chem., 39, 775, 1918. 



