USE  OF  BENZOIN  IN  OINTMENTS. 
35 
that  this  cerate,  when  made  by  the  officinal  formula,  is  very  liable 
to  rancidity,  but  a  portion  made  by  the  above  formula  on  Feb. 
20,  1867,  still  continues  perfectly  sweet  and  unchanged. 
CERATUM  PLUMBI  SUBACETATIS. 
Take  of  solution  of  subacetate  of  lead,  two  fluidounces  and  a 
half. 
White  wax,  four  troyounces. 
Olive  oil,  eight  troyounces. 
Camphor,  thirty  grains. 
Tincture  of  benzoin,  four  fluidrachms. 
Mix  the  wax  previously  melted  with  the  oil ;  then  gradually 
pour  in  the  solution  of  subacetate  of  lead,  and  when  the  mixture 
becomes  melted  remove  it  from  the  fire  and  stir  it  constantly 
with  a  wooden  spatula  until  it  becomes  cool.  Lastly  add  the 
camphor  dissolved  in  the  tincture  of  benzoin  and  mix  them. 
This  cerate,  when  made  by  the  officinal  process,  is  extremely 
liable  to  become  rancid,  and  is  perhaps  the  most  difficult  of  all 
the  cerates  and  ointments  to  keep  unchanged ;  a  portion  made 
by  the  above  process  in  August,  1866,  was  found,  in  May,  1867, 
to  be  perfectly  sweet  and  soft,  and  unchanged  in  every  respect. 
It  was,  however,  at  that  time  stirred  up  and  exposed  more 
thoroughly  to  the  air,  and  at  the  present  time,  although  it  con- 
tinues sweet  and  soft,  it  has  become  slightly  discolored  on  the 
surface. 
The  cerate  made  by  this  process  is  of  the  same  color  as  that 
made  by  the  officinal  process  when  recent,  that  is,  not  perfectly 
white  ;  the  former  retains  its  color ;  the  latter  becomes  whiter  in 
proportion  as  it  becomes  rancid. 
UNGUENTUM  AQU^l  ROSiE. 
Take  of  ointment  of  rose  water,  16  troyounces. 
Tincture  of  benzoin,  4  fluidrachms. 
Rub  them  together  until  they  are  thoroughly  mixed.  This  is 
another  ointment  very  liable  to  become  rancid  by  age  ;  a  portion 
benzoinated  by  the  above  process  in  Feb.,  1867,  still  continues 
perfectly  sweet,  although  slightly  granular  on  the  surface. 
Ointment  of  rose  water,  unless  very  carefully  prepared,  cannot 
be  benzoinated  by  this  process.  The  vessel  in  which  the  oint- 
ment is  made  should  be  kept  in  the  water-bath  until  the  mixture 
