Wells — Complex Chlorides containing Gold. 319 



The analyses were made by dissolving in water, precipi- 

 tating gold with ammonium oxalate in the presence of a 

 little oxalic acid, and precipitating zinc in the boiling fil- 

 trate with sodium carbonate. Both precipitates were col- 

 lected, ignited and weighed in Gooch crucibles. 



Mixtures of Cs 4 Ag 2 Au 2 Cl 12 and Cs 4 ZnAu 2 Cl 12 . — "When 

 the investigation of the first of these compounds was 

 begun it happened that the gold employed in the work was 

 accidentally and unsuspectedly contaminated with a little 

 zinc. This led to perplexing results, for in most cases the 

 zinc compound crystallized with the silver salt, evidently 

 isomorphously, for all the crystals were very black and 

 usually had a perfectly uniform appearance under the 

 microscope. A great many analyses of such crops were 

 attempted, and these showed wide variations in silver 

 which made it appear that several triple salts existed, 

 while attempts to determine cesium in them, either by 

 weighing the chloride or the sulphate, were mysteriously 

 unsatisfactory. Since the pure zinc salt contains only 

 4.61% of that metal there was only a very small amount 

 of it in many of the mixtures, and hence much work was 

 done before it was detected. 



It may be said that a few crops from this impure mate- 

 rial, especially such as were obtained by hot evaporation 

 or by partial cooling, were practically free from zinc and 

 led to the correct formula for the silver salt before the 

 impurity was discovered. 



A few partial analyses of the mixtures, arranged 

 according to their percentages of silver, are given here to 

 show the wide range reached by the experiments, where 

 fractionation was freely used : 



Calculated for Calculated for 

 I II III IV Cs 4 Ag 2 Au 2 Cl 12 Cs 4 ZnAu 2 Cl 12 



Cs 



Ag 10.71 8.80 5.78 1.28 



Zn 



Au.... 26.62 26.44 28.15 27.50 

 CI 



When certain crops containing very little silver, like 

 IV, were obtained some pale crystals were noticed, and 

 then a careful qualitative analysis revealed the presence 

 of the zinc. 



33.90 



37.51 



13.77 



None 



None 



4.61 



25.17 



27.84 



27.16 



30.04 



