206 
NOTES  ON  BENZOIC  ACID  AND  SOME  BENZOATES. 
still  in  contact  with  the  liquid,  together  with  which  they  dry  to 
an  opaque  mass  without  crystalline  structure.  When  removed 
from  the  solution  and  rapidly  pressed  between  bibulous  paper, 
they  preserve  only  in  some  measure  their  original  shape.  The 
brown  syrupy  liquid  as  obtained  by  evaporation,  dries  to  the 
last  drop  to  a  white  opaque  mass.  Benzoate  of  soda  is  best 
obtained  in  crystals,  by  evaporating  its  solution,  only  so  far  that 
on  cooling  it  will  just  commence  to  crystallize,  and  to  expose  it 
gradually  to  a  lower  temperature  ;  the  crystals  thus  formed  by 
cooling  to  32°,  are  to  be  removed  from  the  thin  liquid,  and  rapid- 
ly dried  by  pressing  them  between  folds  of  bibulous  paper. 
Benzoate  of  Iron. — According  to  Trommsdorff  and  Berzelius, 
the  ter-benzoate  of  iron  is  formed  by  dissolving  recently  pre- 
cipitated sesqui-oxide  of  iron  in  an  aqueous  solution  of  benzoic 
acid;  the  yellow  needles  are  decomposed  by  water  and  alcohol, 
leaving  a  basic  salt  behind. 
When  a  concentrated  solution  of  benzoate  of  soda  is  added 
to  the  officinal  solution  of  ter-nitrate  of  iron,  a  voluminous 
orange  colored  precipitate  is  obtained,  which  is  immediate- 
ly thrown  on  a  filter ;  when  the  liquid  has  nearly  all  passed,  a 
small  portion  of  water  is  added  to  displace  most  of  the  ferric 
solution,  and  the  precipitate  is  then  allowed  to  dry,  spread  out 
upon  a  brick  tile.     This  was  used  for  analysis. 
Five  grs.  were  heated  in  a  porcelain  crucible ;  a  little  water 
was  first  given  off,  then  benzoic  acid  sublimed  in  small  white 
crystals  ;  on  increasing  the  heat,  a  brown  liquid  collected  on  the 
cover,  which  congealed  into  brown  colored  scales  having  the 
empyreumatic  odor  and  taste  of  benzoic  acid;  the  residue  was  re- 
peatedly moistened  with  nitric  acid,  and  exposed  to  heat  until 
vapors  ceased  to  be  given  off;  it  then  weighed  0.85  grs.  which  is 
equal  to  17  per  cent. 
Ten  grs.  of  the  benzoate  of  iron  was  repeatedly  treated  with 
a  large  excess  of  ammonia,  the  sesqui-oxide  of  iron  was  well 
washed  upon  a  filter,  then  washed  into  a  tared  capsule,  and 
heated  until  it  ceased  to  lose  weight ;  its  weight  was  1.6  grs. 
—16  per  cent. 
Into  a  glass  tube  weighing  48.1  grs.,  3.08  grs.  benzoate  of  iron, 
were  introduced,  and  exposed  to  the  heat  of  a  water  bath  for 
half  an  hour ;  the  loss  was  only  about  0.02  ;  the  tube  was  now 
