LEIGHTON AND CADY: ANALYSIS OF COUNTERFEIT GOLD DUST. I99 



The amount of chalcopyrite, calculated from the amount of sul- 

 fur was 1.69 per cent. Subtracting this and the gold plated plat- 

 inum flakes leaves 51. So per cent of the alloy having the following 

 composition: 



Iron 7.67 per cent. 



Silver ii-73 



Lead 2.63 



Platinum 17.60 



Copper 54- 67 



Nickel 5.70 



Total 100.00 per cent. 



An alloy was made of this composition which resembled gold 

 somewhat in color and was but slightly attacked by dilute nitric acid, 

 but readily by concentrated nitric acid, leaving a black residue. 



The specific gravity of the original mixture was 14.43. The spe- 

 cific gravity of native gold is from 15 to 19.6. The specific gravity 

 of the platinum flakes was 21.32. They were evidently made by 

 cutting coarse platinum wire into small pieces and hammering them 

 in an iron mortar. 



Experiments on the Solubility of Platinum in Ilydrochloric 

 Add. 



The platinum used in these experiments was pure spongy platinum, 

 prepared by precipitation as ammonio-platinic chlorid, ignition in a 

 stream of hydrogen, and treatment with concentrated hydrocliloric 

 acid, which would dissolve any ammonio-pltinic chlorid that 

 might remain. 



Exp. I. 2.65 grammes of platinum was boiled in an open beaker 

 about six hours. The platinum obtained from the solution was .079 

 grams. This experiment was repeated several times with practic- 

 ally the same results. 



Exp. 2. .25 grammes of platinum was sealed in a hard glass tube 

 with one c. c. of cone, hydrochloric acid. This was heated for 

 about three hours to 200 degrees C. .0113 grammes of platinum were 

 obtained from this solution. 



Exp. 3. .200 grammes of platinum was placed in a tube with one c. 

 c. of hydrochloric acid and hydrochloric acid gas passed into the 

 tube to expel the air. The tube was then sealed and heated for ten 

 hours from 300 to 360 degrees C. The platinum obtained was .023 

 grammes. 



