296    CITRINE  OINTMENT  OF  THE  BRITISH  PHARMACOPOEIA. 
The  material  used  for  the  assay  was  very  carefully  averaged, 
by  pulverizing  about  500  grams  of  the  ore,  after  the  topaz 
crystals  had  been  separated.  A  correction  was  subsequently 
made  in  the  result  of  the  assay  corresponding  to  the  quantity 
of  topaz  removed. 
School  of  Mines,  Columbia  College,  N.  Y.,  Dec.  23. 
— Am.  Jour.  Sci.  and  Arts,  May,  1  §65. 
ON  THE  CITRINE  OINTMENT  OF  THE  BRITISH 
PHARMACOPOEIA. 
By  M.  Donovan,  M.R.I.A.,  etc. 
There  is  no  known  formula  for  preparing  citrine  ointment 
which  will  always  present  the  same  appearance  and  possess  the 
same  properties,  and  a  very  short  time  is  adequate  to  induce 
changes  to  a  certain  amount.  This  ointment  may  be  viewed  as 
a  metallic  soap  mixed  with  that  compound  which  Fourcroy  des- 
ignates oxygenized  pomatum.  Oxide  of  mercury,  like  other 
metallic  oxides,  forms  a  soap  with  the  fatty  acids.  Berthollet 
produced  such  a  compound  by  decomposing  corrosive  sublimate 
by  means  of  solution  of  soap  ;  but  it  was  not  permanent ;  in 
process  of  time  it  became  slate-colored.  A  soap  may  be  formed 
of  an  analogous  constitution  by  heating  finely-levigated  peroxide 
of  mercury  with  lard  ;  but  the  soap -thus  produced  undergoes 
the  same  changes  as  that  of  Berthollet,  first  becoming  brown, 
and  ultimately  slate-colored.  Hence,  the  ointment  of  red  pre- 
cipitate can  not  be  kept  unchanged  in  the  apothecary's  shop. 
Citrine  ointment  is  similarly  acted  on  by  time;  if  its  color  be 
ever  so  bright  a  yellow  at  first,  it  soon  becomes  dull,  and 
by  degrees  tends  to  the  same  alterations  as  those  already  men- 
tioned. 
These  changes  are  induced  by  the  gradual  decomposition 
of  the  mercurial  nitrate  and  evolution  of  the  oxide.  If  the 
decomposition  be  assisted  by  heat,  the  oxide  is  not  only 
evolved  but  decomposed,  and  vapor  of  mercury  is  freely  dis- 
charged. 
Citrine  ointment  is  of  French  origin.  It  was  first  introduced 
at  the  Hotel  Dieu  where  it  was  employed  for  the  cure  of  itch — 
a  disease  which  raged  there  ruthlessly  at  the  time.    The  basis 
