PLATINIZING  METALS. 
127 
must  not  dwell  further  upon  these  interesting  facts  in  the  history 
of  platinum,  for  our  intention  is  to  describe  something  newer  and 
less  known.  We  purpose  giving  the  details  of  a  very  simple  and 
beautiful  process  for  covering  other  metals  with  a  delicate  film 
of  metallic  platinum,  and  so  at  once  varying  their  appearance, 
and  endowing  them  with  one  of  the  virtues  of  this  metal,  namely, 
incorrodibility. 
We  have  before  mentioned  that  although  platinum  does  not 
easily  dissolve  in  acids,  it  can  be  induced  to  dissolve  by  appro- 
priate treatment.  If  a  few  grains  of  scrap  platinum,  which  may 
be  purchased  at  the  rate  of  about  twenty  shillings  the  ounce,  be 
warmed  in  a  flask  with  a  mixture  of  three  parts  of  hydrochloric 
(muriatic)  acid  and  one  part  of  nitric  acid  (aqua  regia),  it  will 
soon  begin  to  disappear,  dissolving  in  the  acids  with  a  red-brown 
color,  not  unlike  that,  of  dark  sherry.  This  liquid  contains  a 
compound  of  the  metal  platinum  with  the  non-metallic  element 
chlorine.  This  compound  is  generally  called  bichloride  of  pla- 
tinum. It  may  be  obtained  in  the  solid  form  by  drying  up,  at  a 
gentle  heat,  the  acid  solution  of  the  platinum  scrap.  This  salt, 
or  compound  of  platinum,  may  be  thus  prepared — 40  grains  of 
the  metal  yielding  about  68  grains  of  the  bichloride  ;  or  it  may 
be  purchased  at  a  very  moderate  price.  It  cannot,  however,  be 
used  directly  and  without  any  further  treatment  for  the  purpose 
we  have  in  view,  namely,  the  plating  (or,  rather,  platinizing)  of 
various  metals.  The  following  directions  will  serve  for  the  prepa- 
ration of  a  suitable  solution  for  this  purpose: 
Dissolve,  in  ounce  of  distilled  water,  60  grains  of  bichloride  of 
platinum  and  60  grains  of  pure  honey.  Add  to  the  above  solu- 
tion three-quarters  of  an  ounce  of  spirit  of  wine,  and  one-quarter 
of  an  ounce  of  ether.  The  mixed  liquids,  if  not  quite  clear,  must 
be  filtered  through  a  piece  of  white  blotting  paper.  The  objects 
to  be  platinized,  which  may  be  of  iron,  steel,  copper,  bronze,  or 
brass,  are  to  be  thoroughly  cleansed  by  washing  them  in  soda, 
then  in  water.  When  they  have  been  dried,  they  require  heat- 
ing over  a  lamp,  to  a  heat  below  redness.  For  this  purpose  they 
may  be  suspended,  by  means  of  a  fine  wire,  over  a  spirit  or  an 
oil  lamp,  in  such  a  way  as  not  to  touch  the  flame.  Suddenly, 
before  they  have  had  time  to  cool,  the  objects  are  to  be  completely 
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