126  •  PLATINIZING  METALS. 
The  impure  liquid  separated  from  tar  oils  in  the  usual  manner 
by  means  of  soda  solution,  is  first  distilled  alone,  so  as  to  get  rid 
of  most  of  the  water  and  H2S.  It  is  then  re-distilled  in  a  per- 
fectly dry  retort  with  1  to  2  per  cent,  of  anhydrous  cupric  sul- 
phate, collecting  the  distillate  in  5  or  6  flasks.  Most  of  the  dis- 
tillate will  crystallize  at  16°  0.,  though  it  is  generally  necessary 
to  drop  in  a  fragment  of  the  solid. 
If  much  H2S  is  "present,  it  should  be  removed  by  boiling,  or 
by  leaving  the  liquid  in  an  open  vessel,  over  night,  previous  to 
distilling  with  the  sulphate. 
Dalta  Square,  Lancaster,  September  25th. — Lond.  Chem. 
Neivs,  Oct.  11, 186T. 
ON  PLATINIZING  METALS. 
By  Prof,  A.  H.  Church,  M.A.,  F.C.S., 
Of  the  Royal  Agricultural  College,  Cirencester. 
Let  us  begin  with  platinum,  one  of  the  least  known  of  the 
"  precious  "  metals.  Precious  it  is  for  several  reasons.  Not 
that  it  is  very  beautiful  in  color  and  lustre,  for  although  it  may 
be  obtained  nearly  as  white  as  silver,  its  appearance  usually  re- 
sembles that  of  pewter  very  closely ;  yet  time  and  experiment 
have  shown  that  it  has  most  valuable  properties.  It  never  tar- 
nishes; no  ordinary  flame,  or  fire,  or  furnace  will  melt  it;  most 
strong  acids  and  many  chemical  salts  do  not  dissolve  or  injure 
it ;  and,  when  you  do  get  it  to  dissolve,  its  solution  forms  a  most 
useful  chemical  test,  or  "reagent,"  as  it  is  called.  Since  the 
year  1741,  when  platinum  was  first  brought  to  Europe,  under 
the  name  of  platina,  or  "little  silver,"-it  has  been  employed  for 
many  different  purposes.  As  it  could  not  be  worked  like  ordi- 
nary metals,  the  Russians,  who  made  coins  of  it,  adopting  the 
plan  invented  by  the  English  chemist,  Wollaston,  submitted  the 
powder  of  platinum,  as  obtained  by  the  chemical  treatment  of 
the  ore,  to  powerful  pressure,  and  to  repeated  blows,  and  also  to 
the  influence  of  a  very  high  temperature.  By  this  process  the 
powder  or  fine  particles  of  the  metal  may  be  made  to  cohere  into 
an  uniform  solid  mass.  It  is  thus  that  platinum  is  fashioned  into 
crucibles  for  chemists,  stills  for  the  purification  of  sulphuric  acid, 
foil,  leaf,  and  wire  for  various  useful  purposes.    But  we  really 
