Amjuner'i^iarm' }        Glycyrrhizin  in  Licorice  Root.  409 
water,  and  sulphuric  acid  added  as  long  as  a  precipitate  forms.  The 
glycyrrhizin  is  washed  wjth  water,  dried  in  the  air  and  dissolved  in 
strong  alcohol.  The  alcoholic  solution  of  the  acid  is  filtered,  the 
filter  paper  washed  with  alcohol,  and  the  solution  evaporated  to  dry- 
ness. The  residue  is  dissolved  in  ammonia,  and  evaporated,  dried, 
and  weighed  in  a  tared  porcelain  dish." 
Diehl  precipitates  gummy  and  mucous  substances  with  a  large 
quantity  of  alcohol.  The  filtered  and  evaporated  alcoholic  extract  is 
dissolved  in  water.  The  quantity  is  not  stated,  and  further,  the 
amount  of  sulphuric  acid  to  be  used  for  precipitation  is  not  given.  I 
also  fail  to  find  any  statement  as  to  how  long  the  precipitate  is  to 
stand,  and  how  much  water  is  to  be  used  for  washing.  In  order  not 
to  obtain  different  results  on  account  of  these  missing  instructions,  I 
supplied  those  which  seemed  to  me  to  be  suitable.  I  dissolved  the 
evaporated  extract  in  60  cc.  of  water,  precipitated  with  5  cc.  dilute 
sulphuric  acid,  and  washed  afterwards  with  50  cc.  water.  Diehl 
now  attempts  a  purification  of  the  precipitated  acid  by  re-dissolv- 
ing in  strong  alcohol,  previously  drying  the  acid  in  air.  If  one  takes 
freshly  precipitated  glycyrrhizic  acid  which  is  not  quite  dry,  and 
treats  it  on  a  filter  paper  with  absolute  alcohol,  one  can  wash  the 
filter  quite  white,  without  any  trouble,  particularly  if  one  warms  the 
alcohol  a  little.  If,  however,  one  makes  the  precipitated  acid  quite 
air  dry,  perhaps  even  in  a  desiccator,  it  is  then  found  that  a  part  of 
the  acid  has  become  quite  insoluble  in  alcohol.  Since  one  can  scarcely 
assume  that  glycyrrhizic  acid,  through  simply  standing  a  few  hours 
in  the  air,  or  in  a  desiccator,  would  be  decomposed,  and  since,  fur- 
ther glycyrrhizic  acid  is  soluble  in  hot  absolute  alcohol,  one  must 
regard  the  residue  remaining  on  the  filter  as  an  impurity.  An  ex- 
planation for  the  different  behavior  of  the  moist  and  dry  acid  toward 
alcohol,  is  difficult  to  find  unless  one  considers  the  possibility  that  the 
very  small  amount  of  water  remaining  on  the  filter  in  the  first  case 
dilutes  the  absolute  alcohol,  and  so  dissolves  the  glycyrrhizin.  Such 
an  influence,  however,  could  only  be  effective  for  a  few  moments, 
since  the  absolute  alcohol  at  once  penetrates  the  filter.  I  must  accept 
as  the  only  possible  explanation,  the  formation  of  a  colloidal  solu- 
tion. In  any  case,  I  am  of  the  opinion  that  this  residue,  which  is  in- 
soluble in  alcohol  and  easily  soluble  in  ammonia  represents  impuri- 
ties in  the  acid.  Since  such  a  purification  is  easy  to  carry  out,  its  use 
in  the  quantitative  determination  is  certainly  to  be  recommended. 
