Am.  Jour.  Pharm.  j 
March,  1909.  f 
Determination  of  Alcohol. 
133 
with  distilled  water  to  100  or  200  c.c,  shaking  with  1  to  5  Gm.  of 
magnesium  carbonate,  kieselguhr,  or  purified  talc,  and  filtering  the 
solution  into  the  distilling  flask,  washing  the  residue  with  enough 
distilled  water  to  make  the  total  volume  of  filtrate  measure  150  or 
250  c.c.  All  this  must  be  done  under  conditions  of  care  and  low 
temperature  to  avoid  loss  of  alcohol  by  evaporation.  If  the  dis- 
tillate after  such  treatment  should  still  be  cloudy  from  suspended  oil, 
after  dilution  to  the  mark,  it  may  be  shaken  with  magnesium  car- 
bonate, filtered,  and  the  specific  gravity  of  the  filtrate  be  taken  as  a 
basis  for  calculation  of  the  alcoholic  strength.  A  better  method, 
however,  and  one  which  will  also  serve  to  eliminate  the  presence  of 
the  fourth  class  of  interfering  substances,  namely  ethereal  solvents, 
will  now  be  given. 
The  presence  of  ethereal  solvents,  such  as  ether  and  chloroform, 
offers  by  far  the  greatest  difficulty  to  be  overcome  in  determining 
the  alcoholic  strength  of  galenical  preparations.  To  such  an  extent 
is  this  true,  that  in  our  laboratory  we  have  surmounted  the  difficulty, 
so  far  as  our  own  preparations  are  concerned,  by  going  around  it, 
as  an  Irishman  might  say.  The  declared  alcoholic  strengths  of 
such  preparations  as  contain  ether,  chloroform,  and  the  like,  are 
calculated  from  the  formulae,  or,  where  this  is  not  possible,  from 
the  determined  alcoholic  strength  of  the  preparation  or  mixture  at 
the  stage  just  prior  to  the  introduction  of  the  ethereal  solvent. 
Thus  the  necessity  for  an  actual  determination  of  the  alcoholic 
strength  of  the  finished  preparation  can  often  be  obviated,  but  it 
still  remains  necessary  to  have  a  satisfactory  method  for  the  exami- 
nation of  such  preparations  from  unknown  sources.  Especially  is 
this  necessary  for  the  proper  enforcement  of  the  Food  and  Drugs 
Act  by  the  Government  authorities. 
The  following  method,  which  has  the  endorsement  of  Dr.  L.  F. 
Kebler,  Chief  of  the  Division  of  Drugs  of  the  Bureau  of  Chemistry 
at  Washington  is  that  of  Thorpe  and  Holmes,  and  has  been  copied 
from  the  Journal  of  the  Chemical  Society,  Vol.  83  (1903),  page  314. 
It  is  the  method  employed  in  the  British  Government  Laboratory. 
Twenty-five  cubic  centimetres  of  the  sample,  measured  at  60  0  F.  (15. 50  C), 
are  mixed  with  water  in  a  separator  to  a  bulk  of  from  100  to  150  c.c.  and 
common  salt  is  added  in  sufficient  quantity  to  saturate  the  liquid.  The 
mixture  is  now  shaken  vigorously  for  five  minutes  with  from  50  to  80  c.c. 
of  light  petroleum,  boiling  below  6o°  C,  and  after  standing  for  about  half 
an  hour  the  lower  layer  is  drawn  off  into  another  separator,  extracted  if 
