THE  AMERICAN 
JOURNAL  OF  PHARMACY. 
DECEMBER,  1886. 
LIQUOR  HYDRARGYRI  NTTRATIS. 
By  Frank  X.  Moeek,  Ph.G. 
Read  at  the  Pharmaceutical  Meeting  November  16th. 
This  officinal  solution  is  defined  as  "  a  liquid  containing  in  solution 
about  50  per  cent,  of  mercuric  nitrate  [Hg(NOs)2 ;  327*7 — HgO. 
N05 ;  161  85]  with  some  free  nitric  acid." 
Shortly  after  the  appearance  of  the  Pharmacopoeia  in  1882,  in  cal- 
culating the  molecular  weights  of  the  officinal  mercury  compounds, 
I  found  that  the  molecular  weight  of  mercuric  nitrate  as  given  in 
the  above  definition  is  incorrect.  According  to  the  table  of  atomic 
weights  in  the  U.S.P.  it  is  323*7  ;  the  atomic  weight  of  mercury  being 
199*7,  nitrogen  14,  and  oxygen  16. 
Recently,  in  making  the  calculation  to  prove  that  the  parts  used 
in  the  preparation  of  this  solution  yielded  the  amount  of  product  as 
given  in  the  definition,  it  was  discovered  that  here  there  was  another 
error.    The  formula  is  : 
Red  oxide  of  mercury,  40  parts. 
Nitric  acid,  45  " 
Distilled  water,  15    "  to  make  100  parts. 
If  the  reaction  which  takes  place  be  first  written  and  then  the 
molecular  weights  substituted  for  the  formula,  we  have : 
HgO+2HN03=Hg(N03)2+H20. 
215*7       126        323*7  18. 
These  figures  tell  us  that,  the  materials  being  pure,  from  every  215*7 
parts  HgO  we  can  obtain  323*7  parts  Hg(N03)2.    Now  in  calculating 
the  amount  of  HgO(]S~03)2  which  can  be  obtained  from  40  parts 
HgO,  we  have  the  proportion  : 
215*7  :  323  7  : :  40  :  X   X  =  60  parts. 
These  60  parts  of  Hg(N03)2  being  present  in  100  parts  of  the 
solution  show  that  the  solution  contains  60  per  cent,  and  not  50  per 
cent.,  as  stated  in  the  definition. 
Two  explanations  for  this  error  may  be  given  : 
1st.    It  was  the  intention  to  form  a  60  per  cent,  solution  and  thus 
the  error  confined  to  a  misprint  in  the  definition,  or 
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