32  WASTE  OF  PLATINUM  IN  SULPHURIC  ACID  MANUFACTORIES. 
ternally.  This  is  doubtless  the  chief,  and  probably  the  only 
source  of  animal  heat. — Am.  Joum.  Science  and  Arts,  jyovem- 
ber,  1866. 
WASTE  OF  PLATINUM  IN  SULPHURIC  ACID  MANUFAC- 
TORIES. 
Some  few  years  ago,  M.  Scheurer-Kestner,  of  Thann,  made 
some  careful  researches  as  to  the  amount  of  the  waste  of  pla- 
tinum in  sulphuric  acid  manufactories  in  which  platinum  alembics 
were  used,  and  he  found  that,  in  an  apparatus  which,  when 
regularly  worked,  yielded  4,000  kilogrammes  of  concentrated 
acid  per  day,  each  1,000  kilogrammes  of  acid  dissolved  and 
carried  away  about  two  grammes  of  platinum,  when  the  acid 
was  tolerably  free  from  nitrous  vapors,  and  as  much  as  four  or 
five  grammes  of  platinum  when  the  acid  was  no  freer  from 
nitrous  vapors  than  it  is  usually.  He  accordingly  recommended 
that  sulphate  of  ammonium  should  always  be  added  to  the  sul- 
phuric acid  in  the  alembic,  that  salt  being  decomposed  by  the 
nitrous  vapors,  and  its  base  combining  with  them  and  thereby 
rendering  them  inert.  He  found  that  the  waste  of  platinum 
was  very  greatly  diminished  when  this  expedient  was  adopted. 
He  found,  too,  that  new  alembics  undergo  less  rapid  waste  than 
those  which  have  been  in  use  for  some  time,  freshly-hammered 
platinum  being  more  compact,  and  so  less  easily  attacked  by 
solvents,  than  platinum  which  has  been  long  in  use.  Another 
most  interesting  fact  which  he  established  is,  that  platinum  con- 
taining iridium  is  much  more  durable  than  platinum  alone.  He 
put  into  a  still  kept  constantly  at  work,  and  so  kept  immersed 
in  boiling  sulphuric  acid  for  two  months,  two  capsules,  one  of 
pure  platinum,  and  the  other  of  platinum  alloyed  with  iridium. 
At  the  end  of  the  two  months  the  capsule  of  pure  platinum  was 
found  to  be  greatly  deformed  and  its  surface  considerably  cor- 
roded, and  to  have  lost  19*66  per  cent,  of  its  weight,  while  the 
capsule  of  iridio-platinum  retained  its  original  form  and  bril- 
liancy of  surface  quite  unimpaired,  and  had  lost  only  8*88  per 
cent,  of  its  weight.  Since  then,  nearly  all  the  platinum  worked 
into  alembics  on  the  continent  has  been  alloyed  with  a  small 
portion  of  iridium, — Journal  of  the  Franklin  Institute,  Decem- 
ber, 1866,  from  Lond.  Mech,  Mag.,  April,  1866. 
