Am.  Jour.  Pharm.  ) 
March,  1909.  j 
Determination  of  Alcohol. 
1.  The  method  is  not  applicable  where  volatile  substances  other 
than  alcohol  are  present. 
2.  The  method  is  not  applicable  when  the  solution  or  residue 
left  after  evaporation  of  the  alcohol  is  not  perfectly  soluble  in  an 
aqueous  liquid,  for  the  reason  that  the  precipitation  of  dissolved 
matter  caused  by  the  change  from  alcoholic  to  aqueous  menstruum 
produces  an  additional  change  in  the  specific  gravity  of  the  liquid. 
Alcohol  being  used  largely  in  galenicals  because  its  solvent  action 
differs  from  that  of  water,  it  follows  that  a  very  large  proportion  of 
pharmaceutical  preparations  will  precipitate  when  their  alcohol  is 
removed  and  will  not  yield  a  clear  solution  again  on  dilution  with 
water.  A  method  eliminating  this  difficulty  is  now  being  worked 
out  in  our  laboratory,  whereby  it  is  hoped  to  increase  greatly  the 
availability  of  this  method.  This  modification  will  be  discussed 
later  on  in  this  paper. 
We  have  left,  therefore,  only  the  third  method,  that  of  distilla- 
tion, which  must  be  adapted  to  use  in  pharmaceutic  preparations. 
Primarily,  we  have  only  two  difficulties  to  surmount  in  applying 
the  method  by  distillation  to  pharmaceutic  preparations.  The  first 
and  principal  difficulty  lies  in  the  possible  presence  of  volatile  sub- 
stances other  than  alcohol  which  would  distil  over  with  the  latter 
and  vitiate  the  specific  gravity  of  the  distillate.  The  second  diffi- 
culty, which  is  a  mechanical  or  physical  one,  consists  in  the  liability 
of  the  solution  to  froth  over,  or  to  carry  non-volatile  matter  mechan- 
ically over  into  the  distillate. 
Taking  up  first  the  greater  difficulty,  that  caused  by  volatile 
substances  other  than  alcohol,  we  can  divide  such  substances  into 
four  classes  as  follows : 
1.  Volatile  Acids. 
2.  Volatile  Alkalies. 
3.  Volatile  oils  and  aromatics. 
4.  Ethereal  Solvents. 
It  is  apparent,  therefore,  that  a  knowledge  of  the  composition  of 
the  preparation  is  essential  before  a  suitable  method  can  be  selected 
for  determining  its  alcoholic  content.  Volatile  oils,  aromatics,  ether 
and  chloroform,  can  generally  be  detected  at  once  by  their  odor,  if 
present  in  amounts  sufficient  to  vitiate  an  alcohol  determination. 
The  presence  of  volatile  acids  and  alkalies  must,  however,  be  quali- 
tatively determined,  if  the  preparation  is  of  unknown  composition, 
