136 
Determination  of  Alcohol. 
[Am.  Jour.  Pharm. 
I     March,  1909. 
Start  the  distillation,  and  so  regulate  the  heat,  keeping  up  a  con- 
stant flow  of  cold  water  through  the  condenser,  as  to  obtain  nearly 
100  c.c.  of  distillate  in  three-fourths  to  one  and  one-fourth  hours. 
Remove  the  receiving  flask  from  the  condenser,  stopper  it,  cool 
or  warm  its  contents  to  exactly  the  same  temperature  at  which  the 
original  preparation  was  measured,  and  at  that  temperature  dilute  it 
to  exactly  100  c.c.  with  distilled  water.  It  may  now  be  cooled,  if  it 
is  desired  to  avoid  calculations,  to  15. 6°  C.  or  25 0  C,  according  to 
convenience,  and  its  specific  gravity  taken  by  means  of  a  Westphal 
balance.  Consult  the  U.  S.  P.  alcohol  tables,  making  any  necessary 
corrections  for  temperature  variations,  and  calculate  the  percentage 
of  absolute  alcohol  by  volume  in  the  distillate.  This  figure  multi- 
plied by  two  gives  the  percentage  of  alcohol  by  volume  in  the 
original  preparation. 
Especial  attention  is  called  to  the  importance  of  obtaining  exactly 
100  c.c.  of  distillate  at  exactly  the  same  temperature  as  that  at  which 
the  original  50  c.c.  of  preparation  was  measured.  A  considerable 
error  would  be  introduced,  for  example,  by  measuring  the  original 
preparation  at  25 0  C,  and  adjusting  the  distillate  at  100  c.c.  at 
150  C.  On  the  other  hand,  the  variation  is  negligible  as  between 
measuring  both  original  preparation  and  distillate  at  150  C.  or 
measuring  both  at  25 0  C.  Moreover,  even  if  the  50  c.c.  of  original 
preparation  were  measured  at  25 0  C.  it  matters  not  that  the  specific 
gravity  of  the  distillate  be  taken  at  150  C,  provided  that  it  was 
adjusted  to  100  c.c.  at  25 0  C.  and  was  not  again  diluted  to  100  c.c. 
after  cooling  to  150  C. 
Having  progressed  more  rapidly  with  the  experiments  looking 
to  the  elimination  of  the  difficulty  in  the  way  of  applying  the  wine 
method  of  alcohol  determination,  mentioned  in  the  early  part  of  this 
paper,  in  which  the  difference  in  gravity  before  and  after  evapora- 
tion of  the  alcohol  and  dilution  to  original  volume  with  water  is 
taken  as  the  basis  for  calculation,  I  shall  now  briefly  outline  the 
experiments  undertaken  and  tabulate  the  results,  although  so  far  few 
in  number,  that  we  have  obtained. 
It  is  scarcely  necessary  to  repeat  that  the  presence  of  easily  vola- 
tile substances,  such  as  ethereal  solvents,  absolutely  precludes  the 
use  of  this  method.  There  remains,  however,  such  a  number  of 
preparations,  the  alcoholic  determinations  of  which  are  rendered 
difficult  by  frothing  and  bumping  (example,  fluidextract  of  sarsa- 
parilla),  together  with  an  equally  large  number,  the  distillation 
