The Precipitation of  K Co [ Au (  CN  ) 2 ] 3 and Similar Cyanoaurate Complexes

Abstract

Hard gold baths, which use cyano-aurate (I) in combination with cobalt or nickel ions, operate close to the solubi l i ty limits of heretofore un-known coordinat ion compounds. This condit ion became evident, earlier, when a pink precipitate was formed after cobalt ions were added to a solution of potassium dicyanoaurate (I) (i). From the ratio of Co:Au = 1:3, it was conjectured erroneously, though in agreement with other authors, that the precipitate contained the cyanides of both gold and cobalt (2). A more elaborate analysis showed, however, that the compound contained potassium, yielding approximately the ratio K:Co:Au = 1:1:3. The compound was consequently subjected to an X-ray dif fract ion analysis and found to exhibit a pattern of lines which is not in agreement with the individual cyanides of cobalt and gold nor with any other catalogued compound. The d-spacings are l isted in Table I.