238 
Ointment  of  Mercuric  Nitrate. 
Am.  Jour.  Pharm. 
May,  1905. 
the  heat  until  effervescence  ceases.  Positively,  at  this  point  in  the 
process,  the  liquid  should  not  be  disturbed  by  stirring.  Now,  when 
all  the  nitric  acid  has  been  decomposed,  the  temperature  can  be 
considerably  raised  without  causing  further  effervescence,  and  the 
liquid  simply  boils.  This  elevated  temperature  may  be  maintained 
for  ten  or  fifteen  minutes,  whereby  the  volatile  fatty  products  will  be 
more  or  less  completely  dissipated.  Then  allow  the  mixture  to  cool 
to  about  400  C.  (1040  F.).  Having  dissolved  the  red  mercuric  oxide 
in  the  remainder  of  the  nitric  acid  without  heat,  by  adding  the 
former  to  the  latter  in  small  portions,  add  this  solution  to  the  nearly 
cooled  fatty  product.  Now  raise  the  temperature  of  this  mixture  to 
6o°  C,  and  maintain  such  until  no  further  evolution  of  gas  takes 
place,  then  withdraw  heat  entirely.  When  the  mass  has  become 
entirely  cold,  mix  thoroughly  by  trituration,  preferably  by  the  use 
of  a  glass  rod. 
The  reaction  in  this  process  for  the  production  of  mercuric  nitrate 
is  as  follows : 
HgO  +  2HNO3  =  Hg(N03)2  +  H20. 
21576  +  12578  =  323-58  ,   +  17-96. 
From  the  above  reaction  it  will  be  apparent  there  still  remains 
an  excess  of  nitric  acid  over  the  amount  required  to  bring  the  red 
mercuric  oxide,  the  equivalent  of  the  amount  of  metallic  mercury  in 
the  official  formula,  into  solution,  but  not  so  greatly  in  excess  as  it 
is  found  in  the  official  process. 
With  the  production  of  mercuric  nitrate  alone  in  this  way,  there 
is  formed  a  little  water,  which,  however,  can  be  of  no  practical 
moment.  It  is  not  at  all  possible  to  introduce  nitrogen  tetroxide 
when  this  solution  is  used,  though  it  does  inevitably  result  from 
the  mutual  decomposition  of  the  fat  and  acid  ;  but  in  the  latter 
instance  its  most  energetic  oxidizing  action  is,  by  reason  of  the 
elevated  temperature,  almost  instantly  utilized.  When,  on  the  other 
hand,  this  substance  is  introduced  at  a  very  much  lower  temperature 
the  finished  product  gives  off  from  the  beginning  rather  disagree- 
able odors. 
Even  by  permitting  a  larger  portion  of  the  nitric  acid  to  react, 
with  the  lard  oil  the  reaction  is  not  final.  Upon  the  addition  of  the 
acid  solution  of  mercuric  nitrate  further  action  takes  place  far  less 
intensely  than  when  the  solution  with  larger  excess  of  acid  is 
