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ON  A  NEW  PROCESS  FOR  ELECTRO-GILDING. 
ON  A  NEW  PKOCESS  FOR  ELECTRO-GILDING. 
By  M.  Briant. 
A  modified  process  for  this  purpose  has  been  proposed  by  a 
M.  Briant,  and  has  been  the  subject  of  a  favorable  report,  made 
by  M.  Jacobi  to  the  Academy  of  Sciences  at  St.  Petersburg.  It 
consists  essentially  in  the  substitution  of  the  oxide  for  the  chlo- 
ride of  gold  in  the  preparation  of  the  gilding-bath,  and  in  the 
employment  of  a  very  feeble  current  of  a  constant  or  sustaining 
battery. 
52  grms.  (=802-88  grs.)  of  gold  are  to  be  dissolved  in  nitro- 
muriatic  acid,  and  the  solution  evaporated,  for  the  purpose  of 
obtaining  the  chloride  of  gold  dry,  and  as  free  as  possible  from 
acid.  This  chloride  is  then  dissolved  in  5  kilogrms.  (=  11  lbs.) 
of  hot  water,  and  100  grms.  (1544  grs.)  of  well-sifted  magnesia 
added,  and  allowed  to  digest  at  a  moderate  temperature.  The 
oxide  of  gold  which  is  separated  is  found  in  combination  with 
the  magnesia.  The  magnesia,  well  washed,  is  then  treated  with 
water  acidulated  with  nitric  acid,  in  the  proportion  of  375  grms. 
of  acid  to  5  kilogrms.  of  water.  The  magnesia  is  dissolved 
by  the  acid,  leaving  the  simple  hydrated  oxide  of  gold,  which 
is  now  thrown  upon  a  filter  and  washed  until  it  is  quite  free  from 
acid. 
It  is  with  the  oxide  of  gold,  thus  prepared,  that  M.  Briant  pro- 
poses to  form  his  bath.    He  takes  of — 
Yellow  prussiate  of  potash   .       .       .       500  grms. 
Caustic  potash  120  grms. 
Water        ......  5  kilogrms. 
To  this  solution  the  oxide  of  gold  with  the  filter  is  added,  and 
the  whole  is  boiled  for  twenty  minutes.  The  oxide  of  gold  dis- 
solves, and  there  is  formed  at  the  same  time  a  precipitate  of 
sesquioxide  of  iron.  It  is  allowed  to  cool,  and  is  then  filtered, 
by  which  a  yellow  liquid  fit  for  use  is  obtained.  The  objects  to 
be  gilded  should  be  well  cleaned,  and  attached  to  the  negative 
pole  of  an  element  of  Daniell's  battery,  while  a  plate  of  platinum 
is  attached  to  the  positive  pole. 
The  gilding  may  be  effected  either  in  a  warm  or  cold  solution  ; 
in  the  first  case  the  deposit  forms  more  rapidly,  but  with  less 
delicacy.    In  order  to  obtain  a  durable  deposite,  analogous  to 
