PREPARATION  OF  MISTURA  FERRI  COMPOSITA. 
195 
green  color  of  the  liquid  before  me.  The  salts  of  copper  would. 
In  this  case,  a  carbonate  of  copper  would  be  formed.  Shortly 
after  receiving  the  "medicine,"  I  poured  it  into  a  coarse  paper 
filter.  After  several  days,  what  did  not  evaporate,  or  remain  on 
the  filter  as  a  residue,  passed  through  as  a  pea-green,  somewhat 
turbid  fluid.  Was  this  residue  on  the  filter,  a  carbonate  of  cop- 
per ?  A  portion  of  it  was  treated  with  nitric  acid,  a  very  obvi- 
ous effervescence  followed  ;  but  the  resulting  liquid  was  not  of 
the  characteristic  color  of  cupreous  salts  in  solution.  Was  this 
owing  to  the  presence  of  organic  matters  ?  Another  portion  of 
the  residue  was,  on  the  affirmative  supposition,  heated  to  the 
charring  point,  and  then  subjected  to  dilute  nitric  acid  :  copious 
effervescence  followed.  After  gently  heating  the  solution,  it 
was  filtered :  the  filtrate  was  greenish  blue,  and  yielded  to  am- 
monia a  splendid  blue ;  and  to  ferrocyanide  of  potassium  an 
abundant  precipitate  of  a  chocolate-brown  color.  Copper  was, 
therefore,  unquestionably  present  in  large  quantity.  What  salt 
of  copper  was  used  ? 
To  a  portion  of  the  first  or  turbid  filtrate  was  added  solution 
of  chloride  of  barium ;  a  milky  appearance  resulted,  but  even 
after  a  long  time,  no  precipitate.  To  the  milky  liquid  strong  ni- 
tric acid  was  added,  and  the  mixture  heated.  By  this  means,  I 
was  gratified  to  find,  I  obtained  a  precipitate  of  all  the  white 
material,  and  a  transparent,  but  colored,  supernatent  fluid  ;  this 
was  decanted,  and  the  precipitate  repeatedly  washed  in  the  test 
tube.  It  was  of  course,  not  soluble  in  nitric  acid,  which  had 
been  added  in  great  excess  ;  nor  was  it  soluble  in  potash.  A 
sulphate  was,  therefore,  clearly  indicated ;  and  the  conclusion 
almost,  if  not  wholly  unavoidable,  tha  t  sulphate  of  copper  had  been 
introduced  into  the  mixture,  instead  of  sulphate  of  iron. 
On  now  testing  the  turbid  filtrate  with  ferro-cyanide  of  potas- 
sium, no  indications  of  iron  were  apparent,  but  abundant  signs 
of  copper  were  manifest.  Ammonia  gave  no  satisfactory  re- 
sults ;  a  bright  needle  suspended  in  it  for  2-i  hours,  was  taken 
out  untarnished  ;  and  sulphuretted  hydrogen  only  blackened  the 
filtrate  without  producing  any  precipitate  after  heating  and  seve- 
ral days  repose  :  thus  showing  the  modifying  and  opposing  influ- 
ence of  the  organic  matters  present,  in  regard  to  all  these  re- 
agents, except  the  ferro-cyanide  of  potassium.  On  acidulating 
the  filtrate,  the  needle  precipitated  an  abundance  of  copper. 
