well's  process  for  copper-plating  iron.  415 
WELL'S  PROCESS  FOR  COPPER-PLATING  IRON. 
This  process  yields  a  coating  of  copper  of  great  brightness 
and  strong  cohesion.  The  object,  whether  of  cast  or  wrought 
iron,  is  freed  from  rust  by  immersion  for  from  five  to  ten  minutes 
in  dilute  muriatic  acid  (2  in  100  water)  and  subsequent  scrub- 
bing for  a  quarter  hour  with  a  wire  brush  and  sand,  then  wash- 
ing in  water  until  all  traces  of  acid  are  removed.  It  is  then 
covered  with  zinc-wire  in  spiral  turns  of  about  six  inches  from 
each  other,  which  also  serves  as  a  means  of  suspension.  The 
bath  consists  of  a  solution  of  caustic  soda  (8  p.  c.)  of  which  11 
quarts  are  mixed  with  50  ounces  of  Kochelle  salts  and  12J  of 
blue  vitriol,  making  a  liquid  of  a  density  equal  to  19°  Beaume\ 
It  retains  its  activity  as  long  as  the  copper  is  kept  replaced,  and 
deposition  from  it  proceeds  with  great  regularity.  The  material 
of  the  vessel  is  best  when  made  of  wood,  lined  with  gutta  percha 
and  covered  with  a  wooden  lid. 
When  the  coating  is  of  sufficient  thickness,  the  object  is  re- 
moved from  the  bath,  first  washed  with  water  slightly  acidified 
with  sulphuric  acid,  and  then  with  pure  water  until  the  disap- 
pearance of  all  traces  of  acid;  after  this  it  passes  into  a  drying 
room  heated  to  132°  F.  The  bronzing,  when  required,  is  ob- 
tained by  a  bath  of  sulphide  of  sodium,  or  by  means  of  the  same 
bath  as  above,  somewhat  modified,  that  is,  by  increasing  the 
proportion  of  copper  to  a  threefold,  in  which  case  the  bath  no 
longer  deposits  copper,  but,  to  all  appearances,  bronze. 
By  reducing  the  points  of  contact  between  the  iron  and  wire, 
though  retaining  the  spiral  turns  at  uniform  distances,  the  de- 
posit gradually  assumes  a  number  of  colors  in  the  following  series, 
viz.  :  orange,  silver-white,  pale  yellow,  golden  yellow,  carmine, 
green,  brown,  and  dark  bronze, 
.  As  soon  as  the  desired  color  is  attained,  the  object  is  washed 
in  warm  water,  and  again  dried  at  132°  F.  Between  each  sub- 
sequent change  of  color  is  an  interval  of  about  five  minutes. 
The  reaction  is  more  decided  when  the  alkaline  reaction  of  the 
bath  is  stronger. 
For  in-door  work  or  ornaments  the  time  of  immersion  may 
vary  from  3  to  72  hours  ;  for  out-door  objects  a  much  longer 
