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COATING  OF  PLATINUM  UPON  GLASS,  ETC. 
PROCESS  FOR  PRODUCING  A  BRIGHT  COATING  OF  PLA- 
TINUM UPON  GLASS,  PORCELAIN,  &c. 
By  Prof.  Dr.  R.  Bcettger. 
The  first  requisite  is  perfectly  dry  platinum  chloride,  entirely 
free  from  acid,  which,  in  a  small  porcelain  mortar,  is  well  tritu- 
rated with  oil  of  rosemary,  to  be  renewed  several  (about  three) 
times,  until  the  brownish  red  chloride  forms  a  black  soft  plaster- 
like  mass,  free  from  undecomposed  chloride.  The  oil  of  rose- 
mary by  combining  with  chlorine,  turns  yellow  ;  it  is  removed 
and  the  residue  is  then  triturated  with  about  five  times  its  weight 
of  oil  of  lavender,  until  the  whole  forms  a  thin,  uniformly  homo- 
geneous liquid,  which  is  set  aside  for  about  half  an  hour,  when 
it  is  ready  for  use. 
This  thin  liquid  is  painted,  by  means  of  a  soft  brush,  in  a  uni- 
form, very  thin,  layer  upon  the  porcelain,  china  or  glass  ;  for 
the  thinner  the  layer  the  more  lustrous  will  afterwards  be  the 
platinum  coating.  All  that  remains  now  to  be  done  is  to  heat 
the  objects  for  a  few  minutes  to  a  very  dull,  scarcely  visible, 
redness,  when,  if  this  temperature  has  not  been  exceeded,  they 
appear  with  a  most  beautiful  silvery  lustre,  without  requiring 
any  additional  labor. 
Should,  through  some  neglect,  the  platinum  coating  be  im- 
perfect, or  should  an  object  have  been  broken,  the  platinum 
may  be  recovered  without  the  use  aqua  regia,  by  the  follow- 
ing extremely  simple  galvanic  process :  The  coated  surface  is 
covered  with  ordinary  muriatic  acid,  and  then  touched  with  a 
zinc  rod  ;  in  consequence  of  the  evolution  of  hydrogen  from  both 
sides  of  the  platinum,  this  is  at  once  separated  as  an  extremely 
thin  film,  which,  notwithstanding  its  specific  gravity,  partly  rises 
to  the  surface.  On  filtering  off  the  muriatic  acid,  the  whole  of 
the  platinum  is  recovered. 
It  is  important  not  to  keep  the  platinizing  liquid  on  hand  over 
a  day,  since  it  deteriorates  on  keeping. 
The  active  portion  of  the  liquid  is  an  organic  platinum  salt, 
which  may  be  obtained  in  faintly  yellow,  small  octohedrons,  on 
carefully  pouring  alcohol  on  a  larger  quantity  of  the  liquid ;  the 
crystals,  on  the  approach  of  a  flame,  burn  with  a  bright  light, 
