366     ON  PREPARING  RED  OXIDE  OF  MERCURY  OINTMENT. 
persons  for  whom  I  had  prescribed  ointment  containing  the  levi- 
gated nitrie  oxide,  and  whose  prescriptions  had  been  made  up  by 
the  first  chemists,  very  obvious  glittering  red  scales. 
Here  is  some  of  the  red  oxide  of  mercury  ointment  of  the 
British  Pharmacopoeia,  and  here  again  is  the  same  preparation, 
except  that  precipitated  has  been  substituted  for  nitric  oxide ; 
you  may  observe  how  much  "smoother"  an  ointment  the  pre- 
cipitated oxide  makes. 
However,  although  the  fine  state  of  division  of  the  particles  of 
the  binoxide  and  the  consequent  "smoothness"  of  the  ointment 
made  from  it  are  strong  presumptive  proofs  in  its  favor,  the 
absolute  proof  of  its  superiority  over  the  nitric  oxide  is  to  be 
found  in  the  fact,  that  patients  who  have  first  made  use  of  the 
latter  and  then  of  the  former,  always  declare,  and  that  without 
any  prompting,  in  favor  of  the  binoxide. 
A  lady  lately  under  my  care  accidentally  underwent  a  three- 
fold change,  from  nitric  oxide  to  binoxide,  and  then  back  to 
nitric  oxide  again.  She  had  suffered  for  the  last  sixteen  years 
from  a  chronic  cutaneous  disease,  which,  notwithstanding  that 
she  had  been  under  treatment  the  greater  part  of  that  time,  had 
slowly  but  steadily  got  worse.  The  irritation  occasioned  by  it 
was  so  intense  and  so  unremitting,  that  it  was  a  constant  source 
of  torment.  In  conjunction  with  other  remedies,  I  directed  the 
use  of  an  ointment  containing  the  nitric  oxide.  Although  con- 
siderable improvement  took  place,  it  did  not  progress  so  rapidly 
as  I  desired ;  finding  this,  I  wrote  for  precipitated  oxide  in  place 
of  nitric  oxide,  the  treatment,  except  in  this  particular,  being 
continued  as  before.  The  result  was  not  only  much  more  de- 
cided relief  from  the  distress  occasioned  by  the  disease,  and  a 
more  marked  alteration  in  its  appearance,  but  the  ointment  was 
praised  as  a  much  more  agreeable  application.  A  short  time 
after  this  alteration  had  been  made,  the  ointment,  whose  color 
was  masked  by  the  presence  of  other  ingredients,  was  acci- 
dentally made  up  by  her  chemist  with  the  nitric  oxide ;  and 
there  being  nothing  in  its  appearance  to  indicate  the  difference, 
it  was  used  as  before,  but  she  complained  that  it  seemed  to  have 
lost  much  of  its  efficacy,  and  the  appearance  of  the  diseased  skin 
confirmed  her  statement.  On  examining  the  ointment  and 
making  inquiry  of  the  dispenser,  the  cause  appeared. 
