Wells — Complex Chlorides containing Gold. 257 



Art. XXIII. — Some Complex Chlorides containing Gold. 

 I. Pollard's Ammonium-Silver- Auric Chloride; by 

 Horace L. Wells. 



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



Since numerous investigations upon double and triple 

 salts have been carried out in this laboratory by the writer 

 and his associates, attention was attracted to the descrip- 

 tion by William Branch Pollard 1 of a new triple chloride 

 to which he gave the formula (NH 4 ) 8 Ag 3 Au 4 Cl 2 3. Since 

 this formula appeared to be a rather complex one, and 

 because Pollard used apparently drastic methods in pre- 

 paring the salt for analysis, including extracting it with 

 ether and heating it sufficiently to volatilize ammonium 

 chloride, a new investigation of it was undertaken. 



The salt was readily obtained, by following Pollard's 

 directions, from a solution of 25 g. of gold in 50 cc. of 

 nitric and 150 cc. of hydrochloric acid, to which were 

 added 30-35 g. of ammonium chloride and 3 g. of silver 

 nitrate dissolved in 10 cc. of water. When a few more 

 crystals of ammonium chloride were added the silver 

 chloride precipitate that was present was gradually trans- 

 formed into the dark triple salt. Then upon heating the 

 salt with its mother-liquor there was a separation of sil- 

 ver chloride which, upon cooling, was replaced by the 

 triple salt. 



This method of preparing the salt for analysis did not 

 appear to be very satisfactory on account of the concen- 

 trated condition of the solution and also on account of the 

 possible danger of the entanglement of silver chloride in 

 the product. It was found in the present investigation 

 that when solutions somewhat similar to the one recom- 

 mended by Pollard were diluted largely, perhaps with an 

 equal volume or more of 1:1, or stronger, hydrochloric 

 acid, it was easy to obtain clear, boiling solutions from 

 which the triple salt could be obtained either by cooling 

 or evaporation to crystallization on the steam-bath, and 

 both methods of preparation, under wide variations of 

 conditions, have been used in obtaining the products for 

 analysis. The crops of crystals were usually washed to 

 some extent by pouring off most of the mother-liquor, 

 diluting the remainder rather largely with hydrochloric 



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



