Amuay^?05arm'}        Ointment  of  Mercuric  Nitrate.  237 
We  come  now  to  the  suggestion1  long  since  offered,  and  at  one 
time  made  use  of,  to  remedy  the  difficulty  in  producing  a  solution 
of  mercuric  nitrate  to  replace  that  in  the  official  formula.2  Rother 
first  suggested  the  use  of  red  mercuric  oxide  dissolved  in  nitric  acid 
to  produce  this  solution.  He  had  also  pointed  out  that  the  solution 
prepared  with  mercury  and  nitric  acid  is  in  reality  one  of  mercuric 
nitrate  and  mercurous  nitrate,  as  our  reactions  above  showed.  He, 
too,  has  been  accused  of  failing  to  state  his  reason  for  using  a  solu- 
tion prepared  by  dissolving  red  mercuric  oxide  in  nitric  acid ;  but  it 
can  readily  be  seen  that  if  we  are  to  have  an  ointment  of  mercuric 
nitrate,  it  were  far  better  we  should  start  with  a  comparative  simple 
solution  and  one  containing  only  mercuric  nitrate,  than  with  the 
complex  solution  containing  mercury  in  both  its  mercurous  and 
mercuric  states. 
This  investigator  has  pointed  out  another  modification.3  In  this 
he  proposes  to  use  a  larger  portion  of  the  nitric  acid  for  the  oxida- 
tion of  the  fat.  By  such  treatment  the  oxidation  of  the  fatty  matter 
proceeds  to  the  utmost  capacity  of  nearly  all  the  available  nitric  acid 
whereby  violent  reaction  upon  the  addition  of  the  nitrate  solution 
to  the  nearly  cold  fat  is  precluded. 
The  formula  to  be  suggested  and  recommended  will,  it  is  hoped, 
appear  as  a  most  logical  deduction,  while  its  manipulation  must 
necessarily  be  productive  of  more  uniform  results.  Notwithstanding 
the  fact  that  it  has  been  commented  on  before,  the  reasons  here 
adduced  in  urging  its  adoption  differ  widely  from  those  used  before.4 
Such  is  the  formula  which  follows  : 
Red  mercuric  oxide  75*5  grammes. 
Nitric  acid  175-  " 
Lard  oil  760*  " 
Heat  the  lard  oil  in  a  clean  glass  or  porcelain  vessel,  to  a  temper- 
ature of  ioo°  C.  (2120  F.),  or  the  dish  may  be  placed  into  a  bath 
of  hot  water  until  the  temperature  of  the  oil  has  risen  to  about 
100°  C.  (2120  F.);  then  withdraw  the  heat,  gradually  add  100 
grammes  of  nitric  acid,  and,  when  the  reaction  moderates,  reapply 
Mother,  Am.  Jour.  Phar.,  Third  Series,  Vol.  18,  pp.  417  et  seq. 
2  England,  Am.  Jour.  Pharm.,  Vol.  69,  pp.  209  et  seq. 
3  Rother,  Am.  Jour.  Pharm.,  Third  Series,  Vol.  18,  pp.  417  et  seq. 
4  England,  Am.  Jour.  Pharm.,  Vol.  69,  p.  211. 
