134  Formic  Acid  in  Acetic  Acid.  {^'^irollmt'^ 
existing  between  the  substance  to  be  analyzed  and  the  form  in  which 
it  is  weighed,  and  from  which  its  percentage  is  computed,  is  greater. 
A  number  of  analyses  were  made  with  sodium  and  copper  formates, 
and  yielded  decidedly  satisfactory  and  constant  results.  The  method 
was :  Take  0*1  to  0*2  gm.  of  the  formate,  2  gm.  HgClg,  1  gm.  NaK 
C^H^Og  and  150  cc.  of  water,  boil  for  one  half-hour,  then  add  10  cc. 
of  hydrochloric  acid,  in  order  to  dissolve  any  oxide  or  tartrate  which 
might  possibly  be  precipitated  through  some  impurity,  filter  through 
a  weighed  filter,  wash  the  precipitate  with  boiling  water  until  the 
washings  cease  to  precipitate  silver  nitrate,  dry  at  100°  C.  and  weigh. 
The  sodium  formate  contained  some  moisture  and  carbonate. 
Amount  taken  Weight  of  Hg 2 CI  2  NaCHOg,  found.  Percentage. 
No.  1.       0.0988                  0.668    "              0.09661  97.78 
No.  2.      0.0988                  0.669                  0.09675  97.90 
No.  3.      0.0988                  0-6685                0.09668  97.84 
The  copper  formate  was  not  pure  containing  sulphate,  and  the  cal- 
culations from  the  weight  of  mercurous  chloride  are  given  as  formic 
acid.    0.178  gm.  of  the  impure  formate  was  taken  in  each  case. 
Weight  of  Hg2 CI 2  Amount  of  HCHO2  Percentage. 
No.  1.       0.973                            0.0952  53.48 
No.  2.       0.972                            0.0951  53.42 
No.  3.       0.971                            0.0950  53.36 
No.  4.      0.976                            0.0955  53.64 
After  thus  showing  the  reliability  of  the  analytical  process,  a  num- 
ber of  samples  of  acetic  acid  and  acetates  were  examined,  and  the 
amounts  of  formic  acid  or  anhydrous  formate  of  the  metal  are  thus 
summarized  : 
Sample.  Percentage. 
No.  1.  No.  8  Acid.  0.642 
No.  2.  U.S.P.  "  0.344 
No.  3.  U.S.P.  0.020 
No.  4.  Glacial  "  0.049 
No.  5.      Na  C2H2O3  (CP.)  0.954 
No.  6.      K  C2H3O2  free,  but  contains  considerable  butyrate. 
No.  7.       Cu  (C2H302)2  "  "         a  trace  of  butyrate. 
No.  8.      Pb(CoH302)2  free. 
No.  9.  Zn  (0211302)2  contains  both  formate  and  butyrate  in  small 
quantities. 
These  examinations  were  carried  out  as  with  sodiuui  and  copper 
formates  using,  however,  lOgm.  of  the  samples.  Especially  in  the 
case  of  the  acids  will  there  be  seen  the  constant  presence  of  formic 
