Am.  Jour.  Pharm.l 
March,  1888.  j 
Formic  Acid  in  Acetic  Acid. 
133 
hour.    The  calomel  formed  was  filtered  off,  thoroughly  washed,  dried 
at  100°  C.  and  weighed. 
Weight  of  Amount  of  Percentage 
Weight  of  Acid.        HgaClg  HCHO^  ofHCHOa 
No.  1.               10-820  gms.              0*240  0  0235  0-22 
No.  2.               10-670    "                0-156  0  0153  0-14 
The  acid  in  other  experiments  was  partly  or  completely  neutralized 
with  sodium  carbonate  before  boiling;  the  precipitate  in  these  cases 
was  black,  and  consisted  of  mercury  and  calomel,  but  greater  in 
amount.  The  hydrochloric  acid  liberated  as  in  the  above  reaction, 
decomposed  the  sodium  acetate  liberating  acetic  acid,  which  does  not 
interfere  with  the  decomposition  of  the  formic  acid. 
Weight  of  Amount  of  Percentage 
Weight  of  Acid.         Hg^Cl^  HCHO2  ofHCHOa 
No.  1.                  10-410                  0-620  0-0606  0*58 
No.  2.                  10-880                  0-624  0  0610  0-56 
Better  results  were  gotten  by  using  ammonium  hydrate  in  quantity 
corresponding  to  the  reaction  : 
2  HgC]2 + 2  NH.OH  +  HCHO^^Hg^Cl  ^ + 2  NH.Cl + 2  H^O + COo, 
or  about  3  cc.  ammonium  hydrate  to  2  gm.  mercuric  chloride. 
Weight  of  Amount  of  Percentage 
Weight  of  Acid.      HgaCls  HCHO2  ofHCHO^ 
No.  1.                  10-560                  0-693  0-0676  064 
No.  2.                  11-230                  0-733  0-0719  0*64 
This  method  yields  constant  results  with  acetic  acids,  but  did  not 
answer  so  well  with  formates.  The  ammonium  hydrate  added  to 
neutral  solutions  containing  mercuric  chloride  gives  a  precipitate  ot 
mercurammonium  chloride.  As  the  addition  of  ammonium  hydrate 
is  solely  for  the  purpose  of  neutralizing  the  hydrochloric  acid  liberated, 
a  number  of  normal  organic  salts  Avere  tried,  through  the  use  of  which 
an  organic  acid  is  liberated  which  has  no  reducing  action  on  mercuric 
chloride.  Of  a  number  used  Rochelle  salt  was  deemed  the  one  best 
suited  in  that  it  could  be  easily  obtained  pure;  using  this  instead  of 
having  tartaric  acid  liberated,  there  is  formed  a  small  quantity  of  acid 
potassium  tartrate  which,  however,  remains  in  solution. 
2HgCl2-H  NaKC.H  A  +  NaCHO,=Hg2C]2+ 2  NaCI + KHC.Hp, 
4-C02. 
The  advantage  of  the  estimation  is  that  46  parts  of  formic  acid  are 
sufficient  to  precipitate  470'2  parts  of  calomel ;  the  delicacy  of  a  quan- 
titative estimation  is  increased  proportionately  as  the  numerical  ratio 
