PURIFICATION  OF  ESSENCE  OF  ALMONDS.  353 
The  cost  of  the  process  may  therefore  be  summed  as  the  me- 
tallic ingredients  and  oiss.  of  spirit,  very  trifling,  considering  the 
importance  of  the  object.  It  is  very  probable  that  the  cost  may 
be  still  further  reduced  by  diminishing  the  quantity  of  iron  and 
potass,  but  as  I  have  not  tried  a  less  quantity,  I  cannot  recom- 
mend its  adoption.  From  an  ounce  of  essence  thus  treated,  I 
obtained,  by  treating  the  mass  in  the  filter  with  hydrochloric 
acid,  ten  grains  of  what  appeared  to  be  pure  Prussian  blue.  Con- 
sidering it  is  such,  and  that  it  does  not  contain  water  (although 
it  is  stated  to  contain  a  small  but  hitherto  unascertained  quantity,) 
assuming  also  that  the  spec.  grav.  of  the  air  is  the  same  as  that 
of  water  (its  real  gravity  is  1.043,  as  stated  in  Turner,)  the  oil 
must  have  contained  11.77  per  cent,  of  prussic  acid ;  but  allow- 
ing the  decimals  for  the  correction  of  errors,  the  essence  contained 
previous  to  treatment  1.1  per  cent,  of  anhydrous  prussic  acid, 
being  therefore  more  than  half  as  strong  as  the  P.  L.  acid.  It 
has  been  asserted  that  the  pure  oil,  hydruret  of  benzoyle,  is  more 
liable  to  be  oxidized  to  benzoic  acid  than  the  crude ;  if  so,  it 
would  be  advisable  to  keep  it  in  well-closed  vessels.  During  the 
process  I  have  not  observed  anything  that  would  indicate  a 
change,  although  such,  in  a  small  degree,  is  very  possible.  I 
would  only  add  that  the  essence  when  carefully  treated  as  de- 
scribed will  be  obtained  without  contamination,  and  rather  improved 
in  flavor  than  otherwise.  I  trust  this  or  some  other  equally  ef- 
fectual method  may  be  generally  adopted,  and  the  public  health 
no  longer  jeopardized  by  the  sale  for  use  in  flavoring  food  of  that 
which  is  a  deadly  poison. 
Mr.  Edwards,  of  Liverpool,  thought  the  subject  of  the  purifica- 
tion of  oil  of  bitter  almonds  from  hydrocyanic  acid  was  one  of 
considerable  importance,  and  that  its  discussion  in  the  presence 
of  practical  and  scientific  men  would  be  productive  of  much  good. 
He  thought  it  was  not  creditable  to  the  state  of  Pharmacy  in  this 
country,  that  in  addition  to  the  variable  strength  of  the  hydro- 
cyanic acid  of  the  three  British  Pharmacopoeias,  there  should  be 
a  preparation  sold  for  culinary  purposes  which  was  nearly  as 
powerful  a  poison  as  the  medicinal  prussic  acid  itself.  Some? 
persons  they  mitigated  the  danger  resulting  from  the  use  of  es- 
sence of  almonds  by  making  it  weaker  than  the  usual  strength, 
but  he  considered  it  important  that  it  should  be  of  uniform 
23 
