26 
Vanillic  Acid. 
(  Am.  Jour.  Phabj®. 
\     Jan.  1,  1873. 
Carles  preferred  to  purify  the  deposit  found  at  the  bottom  of  the  cases 
in  which  vanilla  had  been  kept.  From  a  mixture  of  specimens  from 
various  sources  he  made  a  concentrated  aqueous  solution  by  boiling,, 
and  after  the  addition  of  animal  charcoal,  passed  it  through  a  moist- 
ened filter.  Upon  cooling,  the  acid  was  deposited,  and  it  was  submit- 
ted to  two  or  three  successive  crystallizations.  If  cooled  slowly  the* 
crystals  appeared  as  colorless  transparent  prisms,  sometimes  more 
than  two  centimetres  long.  When  fresh  and  very  pure  their  odor 
was  very  feeble,  but  was  increased  by  heat,  and  their  taste  was- 
piquant.  Vanillic  acid,  so  obtained,  melts  at  between  80°  C.  and  81° 
C.  Heated  on  platinum  foil,  it  volatilizes  without  decomposition,  but 
it  distils  with  difficulty  in  a  retort  at  about  280°  C.  It  is  very  solu- 
ble in  cold  alcohol,  ether,  chloroform,  sulphide  of  carbon,  and  the 
fixed  and  volatile  oils.  Water  at  15°  C.  dissolves  1-2  per  cent.,  but  in 
boiling  water  it  is  very  soluble.  It  decomposes  the  bicarbonates  with, 
effervescence  ;  and  saturates  perfectly  the  alkaline  bases  in  the  cold,, 
and  the  earth  bases  with  heat.  Pure  concentrated  sulphuric  acid  turns 
it  yellow  in  the  cold,  but  if  the  acid  contain  traces  of  nitric  acid  a. 
scarlet  color  is  produced,  and  the  same  result  follows  with  pure  sul- 
phuric acid  and  resinous  crystals.  Dilute  nitric  acid  attacks  it  feebly^ 
but  concentrated  quickly  converts  it  into  oxalic  acid.  Chlorine,  bro- 
mine, and  iodine  yield  products  of  substitution.  It  is  precipitated  by 
acids  from  concentrated  aqueous  or  alcoholic  alkaline  solutions  with 
little  evident  modification,  even  after  being  exposed  for  several  hours 
to  a  temperature  of  100°  C.  It  colors  the  persalts  of  iron  blue,  re- 
duces nitrate  of  silver  and  is  precipitated  plentifully  by  the  acetates 
of  lead.    Its  formula  is  given  by  M.  Carles  as  C16EI806  (CsH80.d). 
Found.  Calculated. 
I.  II. 
Carbon,        .  .    63-14  63-13  63-15 
Hydrogen,    .  .      5-55  5-69  5-26 
The  author  describes  the  following  compounds  of  vanillic  acid  ob- 
tained by  him  : 
Vanillate  of  Lead  (C16H7Pb06). — Tufts  of  white  crystals  radiating, 
from  a  common  centre,  deposited  upon  cooling  after  mixing  a  hot 
aqueous  solution  of  vanillic  acid  and  a  solution  of  neutral  acetate  of 
lead. 
Vanillate  of  Magnesia  (C16H7Mg06).— Colorless,  inodorous  crystals 
