Am'M°ay?Sarm'}       Ointment  of  Mercuric  Nitrate.  233 
the  relative  purity  of  the  two  substances,  the  experience  of  a  large 
manufacturing  establishment  shows  that  the  commercial  metallic 
mercury  is  of  far  greater  uniformity  and  purity  than  the  "  red 
oxide "  of  commerce.  Many  samples  of  the  red  mercuric  oxide 
have  been  encountered,  which  yielded  a  brownish  colored  nitric 
acid  solution  and  left  an  insoluble  residue  resembling  brick-dust ;  so 
that  it  would  be  better  to  use  the  metallic  mercury  in  the  prepara- 
tion of  the  official  solution  of  mercuric  nitrate,  in  order  to  ensure  a 
satisfactory  product.  The  purity  of  commercial  mercury  was,  in  all 
cases  noticed,  very  good;  fin  purifying  156  pounds  only  y 
pound  of  impurity  was  obtained,  or  less  than  y2  per  cent.  The 
use  of  the  red  oxide  of  mercury  was  suggested  first  in  18621,  and 
more  recently  in  1886,  by  R.  Rother,  who  "  finds  advantages  in  the 
use  of  mercuric  oxide  "  without  explaining  what  these  advantages 
are. 
The  suggestion  as  regards  temperature  is  one  of  great  importance, 
as  experience  has  shown  in  the  manufacture  of  a  total  of  hundreds 
of  pounds  by  the  process  outlined  in  the  American  Journal  of 
Pharmacy,  1894,  P-  523>  that  careful  observance  and  control  of 
temperature  is  essential  for  the  production  of  a  satisfactory  product. 
The  directions  might  be  supplemented  by  advising  the  maintenance 
of  the  temperature  at  6o°  C.  until  all  reaction  ceases,  in  order  to 
obviate  the  development  of  the  spongy  condition  so  often  noticed 
in  this  product. 
The  addition  of  glycerin  may  be  advantageous  in  some  respects, 
but  in  the  formula  as  proposed  by  Mr.  England,  the  addition  of  50 
grammes  of  glycerin  to  1,000  grammes  of  ointment  of  officinal 
strength,  reduces  the  percentage  of  mercuric  nitrate  below  that 
required  by  the  U.S. P.;  this,  however,  could  be  easily  remedied  by 
diminishing  the  quantity  of  lard  oil  by  50  grammes. 
It  is  well  for  those  who  have  difficulty  with  officinal  processes  to 
suggest  improvements  for  the  same ;  but  in  the  case  of  citrine  oint- 
ment, it  is  extremely  likely  that  those  who  fail  to  produce  a  satis- 
factory preparation  by  the  U.S.P.  process  would  not  succeed  with 
any  method. 
A  final  consideration,  not  to  be  altogether  ignored,  is  the  raising 
of  the  cost  of  manufacture  of  the  preparation,  which  would  happen 
x  Kyi.  Jour.  Phar.,  34,  p.  394. 
