578  Liquor  Hydrargyri  Nitratis.  {Am'j&§T*Ili 
2nd.  A  mistake  was  made  in  the  calculation  and  a  60  per  cent,  solution 
gotten,  the  properties  of  which  were  ascribed  to  a  50  per  cent,  solution. 
The  specific  gravity  is  the  only  test  given  to  indicate  the  strength 
of  the  solution.  This  is  stated  to  be  2*100.  A  commercial  solution 
of  nitrate  of  mercury  was  found  to  agree  with  the  product  as  fur- 
nished by  the  U.S.P.  formula.  The  specific  gravity  of  the  sample 
was  found  to  be  2-065  at  16°C. 
To  find  the  percentage  of  mercuric  nitrate,  the  mercury  was  esti- 
mated by  taking  1*007  gm.  of  the  solution,  diluting  with  water,  pre- 
cipitating with  hydrogen  sulphide,  collecting  on  a  weighed  filter, 
drying  at  100°C.  and  weighing  as  mercuric  sulphide.  Weight  0  429  gm. 
The  reaction  in  the  precipitation  is : 
Hg(NOs)2  +  H2S=HgS + 2  HM)3. 
323-7        34     231.7  126. 
From  this  can  be  calculated  the  weight  of  Hg(N03)2  which  yielded 
0-429  gm.  HgS. 
231-7  :  323-7  :  :  0'429  :  X   Z=Q-5993  gm.  Hg(NOs)2. 
This  quantity  being  present  in  1*007  gm.  solution,  the  percentage  is 
gotten  by  the  proportion  : 
1-007  :  0-5993  :  :  100  :  X   JT=59'51  per  cent. 
Showing  that  the  commercial  solution  contains  approximately  60  per 
cent,  mercuric  nitrate. 
A  50  per  cent,  solution  was  made  by  substituting  33*32  parts 
HgO  for  the  pharmacopceial  quantity,  40  parts.  This  figure  was 
obtained  as  follows  :  If  323*7  parts  Hg(N03)2  are  formed  from  215*7 
parts  HgO,  then  50  parts  Hg(jST03)2  are  formed  from  33*32  parts  HgO. 
The  formula  is : 
Red  oxide  of  mercury,  33*32  parts. 
Nitric  acid,  45  " 
Distilled  water,  21-68     "      to  make  100  parts. 
The  specific  gravity  of  this  solution  is  1*885  at  17°C.  decidedly 
less  than  that  given  in  the  U.S.P. ,  although  there  is  a  larger  percent- 
age of  free  nitric  acid  present. 
The  percentage  of  mercuric  nitrate  was  estimated  as  under  the 
commercial  sample.  1.075  gm.  of  the  solution  yielded  a  precipitate 
of  mercuric  sulphide,  weighing  0*385  gm.  By  analogous  proportions 
it  was  first  found  that  this  quantity  of  HgS  resulted  from  0*5378  gm. 
Hg(NOs)2,  and  thit  this  corresponded  to  50*03  per  cent.  Hg(N03)2  in 
the  solution. 
