Am.  Jour.  Pharm.  1 
March,  1909.  / 
Determination  of  Alcohol. 
froth  over  or  to  carry  non-volatile  matter  mechanically  over  into 
the  distillate.  Four  things  may  be  mentioned  as  means  of  over- 
coming this  difficulty : 
1.  By  careful  regulation  of  the  heat  employed  and  the  rate  of 
distillation.  For  most  galenical  preparations,  the  heat  should  be 
so  applied  as  to  obtain  a  required  100  c.c.  of  distillate  in  from  three- 
fourths  to  one  and  one-fourth  hours. 
2.  By  avoiding  "  bumping.'''  This  may  be  accomplished  by  the 
employment  of  broken  glass.,  a  few  small  pieces  of  platinum  foil,  a 
few  pieces  of  "  Siedesteinchen  "  (lumps  of  broken  porous  plates), 
or  by  suspending  a  string  in  such  a  manner  as  to  have  it  dip  slightly 
below  the  surface  of  the  liquid. 
3.  By  precipitating  or  coagulating  by  means  of  tannin  or  by 
means  of  lead  subacetate,  certain  substances  which  tend  to  froth. 
4.  When  all  precautions  fail  to  prevent  frothing  over,  the  redis- 
tillation of  the  distillate. 
The  following  directions  for  making  the  alcohol  determination 
of  a  pharmaceutical  preparation  by  distillation  will  serve  to  describe 
the  general  method  employed  in  our  laboratory.  Modifications  of 
the  described  procedure  must,  of  course,  be  made  in  accordance  with 
the  difficulties  already  mentioned. 
Transfer  exactly  50  c.c.3  of  the  preparation  (measured  at  any 
definite  temperature,  that  of  the  room  being  most  convenient)  to  a 
500  c.c.  distilling  bulb  of  the  round-bottomed  variety,  and  1  drachm 
of  tannin  in  such  a  manner  that  none  sticks  to  the  neck  of  the  flask  at 
or  above  the  delivery  tube.  Xext  add  5  to  10  c.c.  of  sodium  hydroxide 
T.  S.,  and  100  c.c.  of  distilled  water.  Rotate  the  flask  until  the  con- 
tents are  thoroughly  mixed,  and  connect  the  flask  with  an  upright 
Liebig's  condenser,  fitted  with  a  spiral  or  worm  condensing  tube. 
The  flask  should  be  supported  by  means  of  a  burette-clamp  on  a 
ring-stand,  to  which  is  also  attached  by  means  of  an  adjustable  clamp 
a  gas  burner  of  the  Argand  type.  This  arrangement  permits  of  a 
ready  adjustment  of  the  heat  applied.  Allow  the  lower  end  of  the 
condenser  tube  to  enter  the  neck  of  a  100  c.c.  graduated  flask,  and 
around  the  mouth  of  the  flask  place  a  wad  of  cotton. 
3  It  is  better  to  take,  of  preparations  containing 
Up  to  30  per  cent,  alcohol  100  c.c. 
From  30  per  cent,  to  60  per  cent,  alcohol   75  c.c. 
From  60  per  cent,  to  80  per  cent,  alcohol   50  c.c. 
And  above  80  per  cent,  alcohol  25  c.c. 
