402  Glycyrrhizin  in  Licorice  Root.        \  Amj J™r  19p2^rm- 
tion  of  ammonium  glycyrrhizinate  leaves  an  insoluble  residue,  after 
it  has  been  evaporated,  dried  at  a  ioo°,  and  taken  up  in  water  again. 
Ammonium  glycyrrhizinate  which  had  been  dried  at  ioo°  (as  it  is 
weighed),  cannot,  without  purification,  be  converted  to  the  barium 
salt.  Glycyrrhizic  acid  dried  at  ioo°  cannot  be  redissolved  in  95  per 
cent,  alcohol  without  leaving  a  residue.  Glycyrrhizic  acid  itself  can- 
not be  converted  to  the  barium  salt  without  purification.  In  the 
barium  salt  obtained,  the  barium  could  be  determined,  and  from  that, 
an  indication  of  the  purity  of  the  salt  could  be  obtained.  But  this 
does  not  result  in  even  an  approximate  estimate  of  the  purity  or 
impurity  of  the  acid  or  ammonium  salt  weighed.  To  all  these  facts 
and  thoughts  can  be  added  the  same  objections  made  against  the 
purity  test  of  HafTner's. 
I  therefore  come  to  the  conclusion  that  it  is  not  possible,  accord- 
ing to  HafTner's  proposal,  or  any  other  methods,  to  determine  the  de- 
gree of  purity  of  the  acid,  even  approximately.  I  cannot  accept  the 
degrees  of  purity  set  up  by  HafTner  for  the  various  acids.  Accord- 
ing to  his  own  results,  he  can  hardly  accept  them — and  if  he  does, 
they  do  not  give  a  true  picture — and  he  offers  no  other  method. 
Although  such  an  exact  determination  of  the  degree  of  purity  is 
very  desirable  and  indispensable  for  a  conclusive  estimate  of  the  in- 
dividual methods  proposed,  one  is  left  to  rely  only  on  the  taste  and 
appearance  as  a  measure  of  control.  It  is  shown  that  the  ammoni- 
acal  extract  undoubtedly  gives  a  less  pure  acid  than  an  aqueous  ex- 
tract, and  for  the  same  reason  the  use  of  alcohol  is  to  be  preferred 
to  a  purely  aqueous  solution.  From  the  appearance  of  the  acid 
weighed,  it  is  to  be  seen  that  a  purification  with  alcohol  according  to 
Diehl  is  important.  The  ammonium  glycyrrhizinate  obtained  by 
Diehl's  procedure  is  of  a  light  brown  color,  while  that  from  the 
other  methods  is  colored  dark  brown. 
Quantitative  Control  of  the  Published  Determinations  of 
Glycyrrhizic  Acid. 
The  Licorice  Used  for  Control  Experiments. 
In  order  to  carry  through  a  critical  work  such  as  the  present,  it 
was  necessary  to  investigate  only  one  kind  of  licorice  extract,  so 
that  the  results  obtained  could  be  compared  with  one  another.  Al- 
though it  might  appear  desirable  to  investigate  the  action  and  ac- 
curacy of  the  individual  methods  proposed,  on  different  kinds  of 
