468 



H. N. Maxson — Small Amounts of Gold. 



I have, however, thought the matter of sufficient interest to 

 warrant further investigation concerning the deportment of 

 this salt under more varied conditions. 



The method employed to determine the rapidity with which 

 the aurous iodide decomposes was as follows : A measured 

 quantity of a standard gold solution was drawn off into a 

 beaker and diluted to the required volume. To this was added 

 the necessary amount of a solution of pure and specially pre- 

 pared potassium iodide, starch was added, and the freed iodine 

 immediately treated with N/100 thiosulphate solution, but 

 only to the rose tint, so that, as in the actual analysis, there 

 might be no decomposing action due to an excess of thiosul- 

 phate upon the aurous salt. 



The time was noted and the mixture allowed to stand until 

 the iodine freed by the decomposition of the aurous iodide had 

 brought the color of the liquid to an ordinary starch blue. 

 The data obtained in this manner are shown in the following 

 table. The gold solution used contained '00048 g. of metal to 

 the cubic centimeter. 











Volume 



Time in 









before the 



minutes neces- 





Gold 



KI 



addition of 



sary to give 



No. 



grm. 



grm. 



thiosulphate. 

 cm 3 



• blue color. 



1 







0144 



0-20 



50 



19 



2 . 







0144 



0-20 



50 



47 



3 







0144 



0-20 



50 



95 



4 



o- 



0144 



0'20 



50 



150 



5 







0144 



0-20 



50 



115 



6 







•0144 



0'20 



50 



82 



7 







0i44 



020 



50 



50 



8 







0096 



0-08 



50 



17 



9 







0096 



0-08 



50 



95 



10 







0096 



0-08 



50 



28 



11 







0096 



0-08 



50 



78 



12 







0096 



0'08 



50 



18 



13 







0096 



0-08 



50 



30 



14 







0096 



0-08 



50 



36 



15 







0096 



0.08 



50 



32 



16 







0048 



005 



50 



45 



17 







0048 



0-05 



50 



168 



18 







•0048 



0-05 



50 



25 



19 







•0048 



0-05 



50 



48 



20 







•0048 



0'05 



50 



43 



21 







•0024 



0-05 



50 



95 



22 







•0024 



005 



50 



105 



23 







0024 



0-05 



50 



135 



24 







0024 



0-05 



50 none in 3 hours 



25 







•0024 



0*05 



50 none in 3 hours 



26 







•0014 



o-oi 



35 



130 



