164  Unguentum  Hydrargyri  Nitratis.  J4^'^™" 
favorable  result,  but  how  far  they  have  succeeded  I  will  leave  to  the 
decision  of  any  of  our  pharmaceutical  brethren,  who  have  closely 
adhered  to  their  instructions.  The  probable  liberation  of  oleic,, 
stearic  and  palmitic  acids  has  been  correctly  pointed  out,  but  what  in* 
such  a  case  became  of  the  glycerin  has  not  been  made  evident. 
The  object  of  obtaining  a  more  definite  idea  of  what  changes  had; 
taken  place,  led  the  writer  of  this  to  dissolve  a  number  of  specimens 
of  the  "  U.  S.  P."  preparation,  partly  his  own  make,  as  also  some 
obtained  from  other  reputable  establishments,  in  petroleum  benzin  and 
ether.  He  was  surprised  to  find  what  small  precipitate  they  afforded,, 
being  only  from  two  to  three  grains  in  sixty  of  the  ointment,  whereas^ 
by  weighing  the  fatty  vehicle  and  the  resulting  preparation,  the  mercurial 
salts  in  the  preparation,  after  liberal  deduction  for  water  present,  should 
not  have  been  less  than  ten  grains  in  each  drachm,  so  that  a  solution 
of  mercuric  oxide  forms  evidently  the  principal  part  of  the  ointment., 
and  the  oxide  can  actually  be  separated  from  it  by  precipitation  with  an 
alkali. 
Why  the  oleate  of  mercury  itself  should  therefore  not  be  preferable 
to  the  ointment  as  a  therapeutical  agent  we  will  leave  to  the  medical 
faculty  to  investigate,  as  certainly  a  more  uniform,  reliable  and  scientific 
preparation  can  be  obtained  by  the  direct  process. 
That  possibly  the  presence  of  stearic  or  palmitic  acids  were  the 
cause  of  the  changes  noted  above,  and  which  make  the  present  form 
of  the  ointment  so  objectionable,  naturally  suggested  itself  to  us,  and 
our  next  step  was  to  procure  oils  which  were  nearer  the  pure  olein. 
Lard  oil,  filtered  at  a  low  temperature,  used  for  that  purpose,  showed 
a  slight  improvement  in  consistency,  but  the  color  of  it  made  it,  if 
anything,  more  objectionable  than  all  the  rest  previously  employed. 
Oil  of  sweet  almonds  fared  no  better,  and  it  then  occurred  to  us  that 
the  fault  of  reducing  the  mercurial  salts  was  not  as  well  with  any  of 
the  fatty  acids  as  with  the  glycerin,  which  in  the  solutions  of  benzin 
and  ether  could  not  be  detected,  although  positively  insoluble  therein, 
so  that  it  must  have  underwent  a  change,  and  there  seems 
reasonable  cause  to  suppose  that  it  was  oxidized  at  the  expense  of  the 
mercurial  salts,  leaving  part  of  them  suspended  in  the  ointment  as  a 
mixture  of  sub-nitrate,  mercurous  oxide  and  globulous  metallic  mer- 
cury, to  all  of  which  the  ointment  owes  its  dirty-green  color,  with 
black  streaks  therein. 
