Chemical Analysis of Counterfeit Gold Dust. 



BY V. L. LEIGHTON AND H. P. CADY. 

 (Read before the Kansas Academy of Science.) 



Some years ago one of the Kansas banks bought a quantity of gold 

 dust, which afterwards was discovered to be an exceeding clever imi- 

 tation of placer gold and was thought to be entirely worthless. A 

 small quantity of it was given one of us a short time ago for analysis 

 when its true character was discovered. 



In appearance it very much resembled placer gold, being composed 

 of malleable irregular shaped flakes mixed with a coarse powder; 

 under the microscope this powder was seen to be composed of two 

 substances of different color and general appearance. One of these 

 was identified as Chalcopyrite (CuFeSg), the other was evidently fine 

 turnings of an alloy. 



The flakes were entirely unattacked by either nitric or hydro- 

 chloric acids, but if treated with nitrohydrochloric acid they immedi- 

 ately lost their yellow color and became white. On further exami- 

 nation these flakes were found to be nearly pure platinum plated with 

 gold. The powder was completely decomposed and partially dissolved 

 by either hydrochloric or nitric acid, giving a blue color to the solu- 

 tion, and leaving a finely divided black residue. To separate the 

 platinum, the mixture was first treated with boiling concentrated 

 nitric acid, carefully washed, and then treated with boiling concen- 

 trated hydrochloric acid, and then with cold dilute nitro-hydrochloric 

 acid, which immediately dissolved the gold plating on the platinum 

 and the residue left from the decomposition of the alloy. 



In working up the various solutions, it was found that the nitric 

 acid solution contained, besides the other metals, a small quantity of 

 platinum. The solution of the platinum in nitric acid was accounted 

 for by the well known fact that an alloy of silver and platinum is 

 readily soluble in nitric acid. The hydrochloric acid solution con- 

 tained a comparatively large amount of platinum, 24 grammes being 

 obtained in working up 1000 grammes of the mixture. That this was 

 not due to nitro-hydrochloric acid formed by nitric acid remaining in 

 the residue, was shown by the fact that the gold plating on the plati- 

 num was entirely unaffected, and it was found that this dissolved im- 

 mediately in cold dilute nitro-hydrochloric acid. 



(197) KAN. UNIV. QtJAB., VOL. Ill, NO. 3, JAN., 1895, 



