130 
Determination  of  Alcohol. 
/Am.  JouP.  rbarm. 
\     March,  1909. 
Text-books  on  analytic  methods  are  replete  with  directions  for 
the  determination  of  the  alcoholic  strength  of  fermented  and  dis- 
tilled liquors.  Here  the  problem  is  a  comparatively  simple  one, 
inasmuch  as  alcohol  is  generally  the  only  easily  volatile  substance 
present  in  amounts  sufficient  to  merit  consideration.  Since  alcohol 
does  not  readily  lend  itself  directly  to  either  gravimetric  or  volu- 
metric methods  of  assay,  nearly  all  determinations  in  the  cases  of 
wines,  liquors,  etc.,  have  been  based  upon  the  influence  of  the  alcohol 
present  upon  the  specific  gravity  of  the  liquid.  In  some  cases,  where 
little  else  than  alcohol  and  water  is  present,  sufficiently  accurate 
deductions  as  to  alcoholic  strength  may  be  made  by  taking  the 
specific  gravity  of  the  original  liquid  and  referring  to  approved 
alcohol  tables.  In  other  cases,  the  difference  in  gravity  before  and 
after '  replacing  all  the  contained  alcohol  with  an  equal  volume  of 
Water  is  taken  as  the  basis  for  calculation.  Again,  a  given  volume 
of  'the  liquid  may  be  distilled  under  proper  conditions  and  the 
specific  gravity  of  the  distillate  taken  as  the  basis  for  the  calcula- 
tion.1 The  problem  before  us,  therefore,  is  to  see  how  these  methods 
may  be  applied  to  galenical  preparations,  and  what  precautions  and 
modifications  it  may  be  necessary  to  adopt  in  specific  cases.2 
In  the  first  place,  practically  all  galenical  preparations  contain 
appreciable  amounts  of  dissolved  substances,  other  than  alcohol, 
which  naturally  affect  their  specific  gravities.  It  follows,  therefore, 
that  the  specific  gravity  of  the  original  preparation  will  not  directly 
indicate  the  alcoholic  strength. 
The  second  method  mentioned,  namely,  that  of  taking  the  specific 
gravity  before  and  after  evaporation  of  the  alcohol  and  restoring  the 
original  volume  by  adding  water,  is  of  limited  application  for  the 
following  reasons: 
1  The  method  based  upon  the  determination  of  the  temperature  of  the 
vapors  produced  on  boiling,  involving  the  use  of  the  ebullioscope,  presents 
difficulties  that  render  it  inapplicable  to  practical  every-day  determinations, 
and  will,  not  be  discussed  in  this  paper.  See  Wiley's  "  Principles  and  Prac- 
tice of  Agricultural  Analysis."  The  method  involving  the  use  of  the  immer- 
sion refractometer  will  be  mentioned  later  on  in  the  paper. 
2  Attention  is  here  called  to  the  fact  that  specific  methods  for  the  deter- 
mination of  alcohol  in  certain  preparations  have  from  time  to  time  been 
worked  out.  Such,  for  example,  is  the  method  of  Pearson  for  the  estima- 
tion of  alcohol  in  concentrated  nitrous  ether,  published  in  the  American 
Journal  of  Pharmacy,  Vol  80  (1908),  page  101. 
