Am'junue?i88^arm' }  Pha rmmeutical  Notes  from  Purdue  University.  285 
without  heat  by  simply  triturating  them  together  and  allowing  them  to 
stand  with  occasional  stirring,  from  one  to  three  days.  It  has  been 
found,  however,  that  the  oleate  of  mercury  is  very  unstable.  It  soon 
deposits  metallic  mercury  on  standing;  the  weaker  the  solution  the 
more  rapid  the  decomposition. 
I  have  made  this  oleate  from  the  yellow  and  also  the  red  oxide  of 
mercury,  with  and  without  heat.  I  found  no  difference  in  the  keeping 
qualities  or  appearance,  and  both  salts  are  similarly  soluble  in  the  acid. 
Sometimes,  however,  trouble  is  experienced  in  dissolving  the  yellow 
oxide,  especially  when  it  is  old  and  has  been  exposed  to  the  light.  Of 
those  made  with  and  without  heat,  I  find  the  latter  keep  longer.  The 
5  per  cent,  and  10  per  cent,  preparations  made  with  heat  began  to  show 
signs  of  decomposition  four  weeks  after  being  made,  while  those  made 
without  heat  were  still  good  and  gave  no  signs  of  change. 
I  also  made  oleate  of  mercury  by  double  decomposition.  The  red 
oxide  of  mercury  was  dissolved  in  excess  in  dilute  nitric  acid  by  boiling, 
filtering  out  the  solution  of  mercuric  nitrate,  and  then  slowly  adding  it 
to  a  filtered  solution  of  soap  with  constant  stirring.  The  solution  first 
becomes  milky,  then  a  precipitate  begins  to  fall ;  the  mercuric  nitrate 
is  added  until  the  solution  becomes  very  nearly  clear  again,  this  leaves 
a  slight  excess  of  the  soap  in  solution.  The  precipitate  is  now  washed 
with  warm  water  and  dried.  Thus  prepared  it  is  of  a  light  yellow  or 
cream  color,  very  nearly  white,  of  a  rather  stiff  consistence  and  contains 
28  per  cent,  of  oxide  of  mercury.  It  keeps  very  well.  A  10  per  cent, 
oleate  of  mercury  made  from  this  differs  somewhat  in  appearance  from 
the  other,  having  a  much  clearer  yellow  color,  while  those  that  are  made 
by  combining  the  oxide  of  mercury  and  oleic  acid,  have  a  whitish 
milky  appearance,  which  I  suppose  is  due  to  the  water  formed  in  the 
reaction  and  which  remains  in  the  finished  oleate. 
The  oleates  made  by  double  decomposition  keep  very  well  if  care- 
fully made,  but  the  method  by  direct  combination  is  recommended,  as 
it  takes  less  time  and  care.  The  soap  solution  necessary  for  making 
oleates  by  double  decomposition  is  best  made  by  taking  a  good  quality 
of  oleic  acid  and  adding  just  enough  solution  of  sodium  hydrate  to 
saponify  it,  the  slight  excess  of  sodium  hydrate  being  neutralized  with 
tartaric  acid.  It  is  best  to  use  this  solution  rather  dilute,  about  eight 
ounces  of  water  to  one  ounce  of  oleic  acid.  The  other  officinal  oleates 
can  best  be  made  by  precipitating  the  soap  solution  with  some  soluble 
salts,  as  sulphate  of  copper,  acetate  of  lead,  acetate  of  zinc,  etc. 
