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FLUORIDE OF GOLD.
                     BY VICTOR LENHER.
  Inasmuch as fluorspar is frequently associated with gold if
nature, and quite notably so in the deposits of the telluride ores,
it has seemed important to study gold fluoride in order to do.
termine if possible whether this substance can play any part
in the genesis of these deposits.
  The known compounds of gold with the halogens, chlorine,
bromine and iodine, are, as a rule, fairly well defined. In
the trivalent condition gold forms the relatively stable chloride
while the bromide and iodide show greater tendency to break
down into the lower state of valence of gold.
  The halides; in which gold shows a monovalence have received
considerable attention, and it is known with a reasonable de.
gree of certainty under what conditions aurous chloride, brom-
ide, and iodide are capable of existence.
  While the chlorides, bromides and iodides of gold have re-
ceived more or less studv, comparatively little is known of fluo-
ride of gold. Prat (Comptes Rendus, 70, 843) has prepared
an intermediate oxide of gold, Au.2 02, by the incomplete So-
lution of gold in aqua regia, in which the hydrochloric acid is
in excess, treated the solution with sufficient bicarbonate of po-
tassium to dissolve the precipitate formed and warned the clear
orange-yellow solution to 950 when a dark olive green precipi-
tate was obtained which when dried showed the composition
AU202. In studying the properties of this oxide, Prat states
that hydrofluoric acid combines with it but without dissolving
it. In his study of the action of fluorine on the various metals,
Moissan states that at a red heat, gold is attacked by fluorine