274 Maxson — Determination of Small Amounts of Gold. 



The application of such a method for the determination of 

 gold naturally starts with that element. The weighed amount 

 of metal, contained in a clean porcelain crucible, can be readily 

 brought into solution with the aid of chlorine water or aqua 

 regia and the excess of the solvent evaporated off upon the 

 water bath. Experiments have shown that a gentle preliminary 

 heating of the solution of the auric salt hastens the rapidity of 

 the reduction. Care must be taken not to reduce any of the 

 gold chloride by such a procedure. 



If traces of electrolyte are present the coagulation of the 

 "red" gold may be sometimes avoided by the addition of a 

 few drops of ether to the cold solution. When small amounts 

 of the metal are handled the volume of the solution should not 

 exceed a few cubic centimeters, and only a small amount of 

 the aqueous solution of acetylene should be added ; otherwise 

 the coloration may be partially or totally inhibited. 



In conclusion, it can be seen from the evidence of the experi- 

 ments described above, that the colorimetic estimation of small 

 amounts of gold is quantitatively possible if proper precautions 

 are taken to ensure the maximum coloration and exclusion of 

 electrolytes. The method is quick and simple in character, 

 and for the amounts of. gold used above, the results show it to 

 possess suitable accuracy for the correct estimation of small 

 amounts of the metal. 



The author wishes to acknowledge his indebtedness for much 

 helpful aid and advice in this, and in previous work, to Pro- 

 fessor Gooch, at whose suggestion these experiments have been 

 carried on. 



