Am'oc°tU.ri  ^8arm" }     Evaluation  of  Balsam  of  Tola.  719 
THE  EVALUATION  OF  BALSAM  OF  TOLU.1 
By  T.  Tusting  Cocking  and  James  D.  Kettle,  B.Sc,  F.I.C. 
It  has  been  pointed  out  by  several  observers  that  the  method  of 
the  British  Pharmacopoeia,  1914,  for  the  estimation  of  the  balsamic 
acids  in  balsam  of  tolu  is  unsatisfactory.  The  results  obtained  are 
low,  as  much  of  the  aromatic  acid  present  is  combined  with  resin 
alcohols  and  is  insoluble  in,  and  thus  not  extracted  by,  carbon  di- 
sulphide. 
In  1914  we  described  a  process  for  the  evaluation  of  benzoin, 
by  which  the  balsamic  acids  could  be  separated  from  the  resinous 
matter,  and  the  free  and  combined  benzoic  and  cinnamic  acids  de- 
termined.2 
The  original  experiments  leading  up  to  this  process  were  carried 
out  on  balsam  of  tolu,  and  the  method  was  afterwards  applied  to 
both  benzoin  and  storax, -the  results  of  the  former  being  published.3 
The  method  (now  official  in  the  British  Pharmacopoeia,  1914)' 
adopted  for  the  estimation  of  the  aromatic  acids  in  the  case  of 
storax3  was  tried  on  balsam  of  tolu  but  abandoned,  as  repeated  ex- 
tractions by  boiling  with  water  caused  the  resinous  matrix  to  become 
so  stiff  and  intractable  that  it  was  impossible  to  extract  the  acids 
completely. 
Boiling  out  of  the  aromatic  acids  with  magnesium  oxide  and 
water,  in  the  presence  of  a  small  quantity  of  xylene  to  soften  the 
resinous' matter,  was  found  to  be  the  most  satisfactory  way  of  deal- 
ing with  the  balsam.  The  magnesium  salts  of  the  aromatic  acids 
are  readily  soluble  in  cold  water,  those  of  the  resin  acids  being  in- 
soluble. A  complete  separation  is  effected  and  the  aromatic  acids 
are  obtained  in  a  purer  condition  than  by  aqueous  extraction  alone. 
The  mode  of  procedure  is  as  follows : 
1.  Free  Balsamic  Acids. — Five  Gm.  of  the  balsam  are  dissolved 
in  25  Cc.  of  hot  alcohol  in  a  250  Cc.  C02  flask,  5  Gm.  of  light  mag- 
nesium oxide,  and  20  Cc.  of  xylene  are  added,  and  the  flask  shaken 
round  until  the  contents  are  well  mixed.    One  hundred  Cc.  of  water 
1  Communication  to  the  British  Pharmaceutical  Conference  for  publica- 
tion in  the  "Year  Book  of  Pharmacy"  for  1918. 
Reprinted  from  The  Pharmaceutical  Journal  and  Pharmacist,  July,  1918. 
2  Y.  B.  P.,  1914;  355. 
3  C.  &  D.,  March  16,  1912,  and  May  25,  1912. 
