28
Book  II.
Division  II.
Preparation. -


SALTS  OF
muriat  of  gold  occasions  a  purple  precipitate,  consisting ¬
  of  gold  reduced  to  the  state  of  purple  oxide.  For
these  interesting  results  we  are  indebted  to  Pelletier  and
Proust.  They  afford  a  sufficient  key  to  explain  all  the
singular  changes  produced  upon  the  greater  number  of
metallic  salts  by  this  muriat  *.
2.  Oxy-muriat  of  tin  This  salt  may  be  formed  very ¬
  conveniently  by  the  process  first.  proposed  by  Pelletier, ¬
  which  consists  in  causing  oxy-muriatic  acid  gas  to
pass  into  a  solution  of  muriat  of  tin  till  it  be  saturated,
and  then  to  expel  the  excess  of  acid  by  heat.  But  it
was  known  long  before  this  process  was  thought  of,
and  was  usually  distinguished  by  the  name  of  smoking
liquor  of  Libavius;  because  Libavius,  a  chemist  of  the
16th  century,  was  the  discoverer  of  it.  When  equal
parts  of  amalgam  of  tin  and  oxy-muriat  of  mercury
are  triturated  together,  and  then  distilled  in  a  retort
with  a  very  moderate  heat,  there  passes  first  a  colourless ¬
  liquid,  consisting  chiefly  of  water,  and  afterwards  a
white  vapour  rushes  all  of  a  sudden  into  the  receiver.
This  vapour  condenses  into  a  transparent  liquid,  which
exhales  a  heavy  dense  smoke  when  exposed  to  the  air,
but  does  not  smoke  when  confined  in  close  vessels.  This
is  the  fuming  liquor  of  Libavius,  or  oxy-muriat  of
tin.
The  theory  of  the  process  is  obvious  :  The  tin  abstracts ¬
  oxygen  from  the  mercury,  and  at  the  same  time
combines  with  the  muriatic  acid.  Muriats  of  mercury
and  of  tin  are  also  formed,  and  line  the  neck  of  the  retort ¬
  mixed  with  a  quantity  of  pure  mercury;  and  there
*  Pelletier,  Ann.  de  Chim.  xii.  225.—  Proust,  Jour.  de  Pbyr.  li.  173.
Composed  of  two  parts  of  tin  and  one  of  mercury.