132 
Determination  of  Alcohol. 
f  Am.  Jour.  Pharai. 
\     March,  1909, 
and  not  only  must  free  volatile  acids  and  free  volatile  alkali  be 
guarded  against,,  but  their  presence  in  form  of  neutral  salts  must 
be  known.  Thus  ammonium  chloride  may  readily  vitiate  a  deter- 
mination, since  (as  will  be  seen  later )  it  is  generally  necessary  to 
distil  from  an  alkaline  or  an  acid  solution;  and  in  the  presence  of 
ammonium  chloride,  the  gravity  of  the  distillate  from  alkaline  solu- 
tion would  be  vitiated  by  ammonia  (NH3),  while  that  from  acid 
solutions  would  be  vitiated  by  hydrochloric  acid  (HC1). 
Preparations  of  vegetable  drugs  generally  contain  larger  or 
smaller  amounts  of  volatile  acids.  The  general  rule,  therefore,  in 
the  cases  of  all  fluidextracts,  tinctures,  etc.,  is  to  distil  from  a  solu- 
tion made  alkaline  with  caustic  soda  or  potash.  This  serves  to 
"  fix "  and  retain  volatile  acids,  and  for  the  greater  number  of 
galenical  preparations  is  the  only  precaution  necessary  to  overcome 
difficulty  Xo.  I. 
On  the  other  hand,  preparations  containing  ammonia  must  be 
distilled  only  after  the  addition  of  an  excess  of  sulphuric  acid  which 
serves  to  "  fix  "  the  ammonia  in  the  form  of  ammonium  sulphate. 
But,  on  the  other  hand,  if  the  sulphuric  acid  serves  also  to  liberate 
and  thus  render  volatile  any  combined  volatile  acid,  either  directly 
from  the  drug  extractive  present  or  from  a  salt  of  ammonia  such  as 
ammonium  chloride,  then  the  first  distillate  must  be  rendered  alkaline 
with  caustic  soda  or  potash  and  be  redistilled. 
When  volatile  oils  and  aromatics  are  present  in  galenical  prepa- 
rations in  amounts  only  sufficient  to  flavor  them,  the  vitiation  of 
specific  gravity  in  the  distillate  is  so  slight,  that  for  the  practical 
purpose  of  obtaining  a  figure  which  will  comply  with  the  require- 
ments of  the  law  as  to  declaration  of  alcoholic  strength,  it  may  be 
considered  negligible.  On  the  other  hand,  distillates  from  alcohol 
solutions  of  volatile  oils,  and  from  fluidextracts  and  tinctures  of  the 
volatile-oil-containing  and  oleoresin-containing  drugs,  often  hold 
in  solution  or  cloudy  suspension  such  an  amount  of  volatile  oil  as  to 
decidedlv  vitiate  the  result.  Spirit  of  anise,  cinnamon,  etc.,  and 
fluidextract  of  sandalwood,  cubeb,  capsicum,  peppermint,  etc..  afford 
good  examples  of  this  class  of  preparations. 
Here,  obviation  of  the  difficulty  is  aided  by  the  fact  that  the 
alcoholic  strength  of  such  preparations  is  always  high — thus  enabling 
us  to  dilute  the  preparation  with  water,  which  throws  out  of  solution 
a  large  percentage  of  the  dissolved  oil.  One  method  of  preparation 
for  the  distillation  of  such  solutions  consists  in  taking  25  c.c,  diluting 
