72o  Evaluation  of  Balsam  of  Tolu.    { Am-^tu\^rm- 
are  now  added,  the  flask  connected  to  a  reflux  condenser  and  boiled 
for  one  hour.  After  cooling,  the  whole  is  poured  on  a  Buchner 
filter,  and  the  aqueous  portion  of  the  filtrate  separated  from  the 
xylene  layer,  which  is  returned  to  the  flask  together  with  the  filter 
paper  and  adhering  magnesia-balsam  magma.  A  second  100  Cc.  of 
water  is  added,  and  the  flask  again  boiled  for  an  hour,  when  the 
aqueous  portion  of  the  filtrate  is  separated  as  before  and  the  extrac- 
tion carried  out  a  third  time.  The  bulked  aqueous  liquids  are 
washed  once  with  20  Cc.  of  ether,  then  rendered  acid  with  hydro- 
chloric acid,  and  the  precipitated  acids  extracted  by  shaking  out 
with  ether.  The  greater  part  of  the  ether  is  distilled  off,  and  the 
residual  aromatic  acids  dried  in  vacuo  over  sulphuric  acid  and 
weighed. 
2.  Total  Balsamic  Acids. — 2.5  Gm.  of  the  balsam  are  saponified 
by  boiling  with  excess  of  alcoholic  potash :  most  of  the  alcohol  is 
then  evaporated  off,  the  residue  dissolved  in  100  Cc.  of  hot  water, 
and  sufficient  hydrochloric  acid  added  to  render  the  whole  slightly 
acid.  Five  Gm.  of  light  magnesium  oxide  and  20  Cc.  of  xylene  are 
next  added,  and  the  whole  boiled  up  under  a  reflux  condenser  for 
1  hour.  The  aqueous  liquid  is  separated,  the  extraction  twice  re- 
peated, and  the  bulked  aqueous  liquids  treated  as  in  the  case  of  the 
free  balsamic  acids. 
The  proportion  of  cinnamic  acid  is  determined  by  the  gain  in 
weight  on  bromination,  details  of  which  may  be  found  in.  our 
previous  note.2  • 
The  aromatic  acids  obtained  from  balsam  of  tolu  are  not  quite 
so  pure  as  those  from  benzoin  and  storax.  The  brominated  acids 
from  the  two  latter  are  white  and  pleasant  smelling,  while  those 
from  tolu  are  slightly  brown  in  color,  and  contain  a  substance 
which  is  extremely  pungent  and  lachrymatory. 
Balsam  of  tolu,  as  a  rule,  contains  very  little  that  is  not  soluble 
in  alcohol,  but  occasionally  samples  are  met  with  containing  woody 
matter.  Three  such  samples  contained  1.6,  8.9,  and  9.0  per  cent,  of 
insoluble  matter. 
Moisture,  generally  present,  was  estimated  by  spreading  in  a 
thin  layer  on  a  sheet  of  glass  and  drying  in  vacuo  over  sulphuric 
acid.  Amounts  varying  from  2.0  to  8.6  per  cent,  were  found,  and 
the  dried  balsam  was  usually  quite  brittle. 
The  determination  of  the  acid  value  of  the  balsam  is  somewhat 
