ON  THE  PURIFICATION  OF  ESSENTIAL  OIL  OF  ALMONDS.  147 
line  bisulphites  ;  hydride  of  benzoyl,  possessing  as  it  does  the 
characters  of  an  aldehyd,  being,  in  fact,  the  aldehyd  of  the 
benzoyl  series,  is  no  exception  to  this  rule. 
If,  therefore,  the  crude  essence  of  almonds  be  shaken  up  with 
three  or  four  times  its  volume  of  a  tolerable  strong  solution  of 
bisulphite  of  soda  and  then  allowed  to  rest,  the  mixture  becomes 
warm  and  the  hydride  of  benzoyl  is  all  converted  into  a  crys- 
talline mass,  having  the  composition  represented  by  the  follow- 
ing formula, — C14H5Na02,S204,3Aq.  These  crystals  removed 
from  the  mother-liquor,  which  should  be  preserved,  drained,  and 
dried  at  a  very  gentle  heat,  and  then  dissolved  in  water,  car- 
bonate of  soda  in  excess  added,  and  the  mixture  distilled,  yield 
hydride  of  benzoyl  in  a  condition  of  absolute  purity.  By  this 
plan,  theoretically  speaking,  there  is  no  loss  beyond  the  actual 
impurities  of  the  crude  substance.  This  is  certainly  a  recom- 
mendation, but  a  little  trouble  is  involved  in  the  double  opera- 
tion of  preparing  the  crystals  and  their  subsequent  decompo- 
sition. 
Having  obtained  the  purified  essence  of  almonds  by  any  pro- 
cess that  is  most  efficient,  another  desideratum  is  felt  in  the  diffi- 
culty of  preserving  it  from  undergoing  that  oxidation  and  change 
with  which  every  one  is  familiar.  By  exposure  to  the  air,  as 
every  one  knows,  absorption  of  oxygen  occurs  and  the  liquid 
hydride  is  converted  into  crystalline  benzoic  acid, — 
and  this  change  proceeds  much  more  rapidly  with  the  purified 
than  with  the  unpurified  oil. 
For  this  defect  there  is  a  simple  remedy,  which  I  think  is  as 
efficient  as  anything  of  the  kind  can  ever  be  expected  to  be.  It 
is  well  known  that  in  the  presence  of  moisture  oxidation  is 
effected  with  infinitely  greater  facility  than  otherwise.  Numer- 
ous examples  of  this  may  be  easily  adduced,  but  I  can  remem- 
ber none  more  striking  than  the  formation  of  rust  upon  the 
surface  of  iron.  If  then,  the  purified  essence  of  almonds  be 
perfectly  dried  by  a  lump  of  chloride  of  calcium  introduced  into 
it,  the  oxidation  is  retarded  in  a  very  marked  degree.  I  can- 
not say  that  the  essence  attains  the  degree  of  permanence  en- 
joined by  the  crude  substance,  but  certainly  the  improvement 
is  of  the  most  decided  character. — London  Pharm.  Journal. 
