Amjufy ri^farm" }        Glycyrrhizin  in  Licorice  Root.  473 
hours,  the  mixture  is  filtered  and  the  insoluble  matter  on  the  filter 
is  washed  with  successive  small  quantities  of  60  per  cent,  alcohol, 
totaling  50  cc.  The -filtrate  and  washings  are  freed  from  alcohol  on  the 
water  bath,  and  evaporated  to  about  30  cc.  The  residue  is  transferred 
to  an  Erlenmeyer  flask,  graduated  at  50  cc,  the  dish  washed  out 
with  water,  and  the  contents  of  the  flask  made  up  to  the  mark;  5  cc. 
dilute  sulphuric  acid  are  added  with  stirring,  and  the  mixture  allowed 
to  stand  one  hour  at  room  temperature,  followed  by  24  hours  on  ice. : 
The  acid  sticking  to  the  bottom  is  brought  quantitatively  on  to  a  fil- 
ter, and  washed  carefully  with  15  cc.  of  2  per  cent,  sulphuric  acid. 
The  filter  is  then  washed  with  15  cc.  ice  cold  water,  saturated  with, 
ether.  The  filter  is  dried  over  sulphuric  acid  at  room  temperature 
in  a  vacuum  desiccator,  and  then  extracted  five  times  successively, 
with  20,  20,  10,  10,  10  cc.  of  hot  95  per  cent,  alcohol  in  the  Erlen- 
meyer flask.  The  solutions  are  filtered  into  a  tared  dish,  the  filter 
washed  with  15  cc.  hot  alcohol,  and  the  filtrate  evaporated  on  the 
water  bath,  and  the  residue  dried  at  a  ioo°  to  constant  weight. 
The  liquid  poured  off  from  the  precipitate  is  united  with  the 
wash  waters  and  after  neutralizing  with  ammonia,  is  evaporated  to  a 
thick  syrup.  This  is  transferred  to  a  glass  cylinder,  and  the  evapor- 
ating dish  is  washed  out,  making  up  to  a  mark  at  18  cc. ;  2  cc.  dilute 
sulphuric  are  added  with  shaking.  It  is  allowed  to  stand  one  hour  at 
room  temperature,  and  24  hours  on  ice.  The  supernatant  liquid  is 
poured  off,  the  precipitate  brought  on  a  filter,  and  washed  with  5  cc. 
2  per  cent,  sulphuric  acid,  and  10  cc.  ice-cold  ether-water,  drop  by 
drop.  The  residue,  dried  in  the  vacuum  desiccator,  over  sulphuric 
acid,  is  extracted  with  10,  10,  5  cc.  hot  95  per  cent,  alcohol,  the  ex- 
tract filtered  into  a  tared  dish,  the  filter  washed  with  5  cc.  hot  alco- 
hol, and  the  filtrate  evaporated  on  the  water  bath.  The  amount 
obtained  after  drying  is  added  to  the  portion  obtained  above.  The 
sum  of  the  two  represents  the  total  glycyrrhizic  acid  in  5  g.  licorice 
extract. 
In  this  method  I  have  taken  particular  account  of  practical  re- 
quirements. In  my  opinion,  it  is  going  too  far  to  require  that  the  in- 
soluble residue  shall  be  washed  until  colorless.  This  is  extremely 
difficult.  In  one  experiment  I  washed  the  filter  with  50  cc,  and  since 
the  filtrate  was  still  colored,  a  further  100  cc  was  poured  through. 
These  100  cc,  however,  upon  evaporation  gave  only  a  very  slight 
film  of  light  yellow  color,  which  can  have  no  practical  influence  on 
the  result. 
