460  Glycyrrhizin  in  Licorice  Root.  \AmjliyT'miaTm' 
so.  He  further  objects  to  Erikson  precipitating  the  glycyrrhizin 
present  in  2  g.  licorice,  from  as  much  as  60  cc.  of  water,  as  this  en- 
tails a  serious  loss  through  solubility.  Linz  claims  that  the  ques- 
tion :  Is  glycyrrhizin  quantitatively  decomposed  by  hydrolysis  ?  is  as 
yet  unsolved. 
Linz  then  conclusively  proves  that  Tschirch's  method  of  hydrol- 
ysis with  Fehling  solution  does  not  work. 
After   4  hrs.  heating  Linz  obtained  0.0388  CuO  —  0.054  g.  glycyrrhizin. 
8    "  "        "         "  0.1078  CuO  =0.109  g. 
"     12   "  "        "         "  0.2941  CuO  =  0.302  g.  " 
"     15    "  "        "         "  0.3041  CuO  =  0.3 12  g.  " 
When  Linz  makes  a  blank  experiment,  without  any  glycyrrhizin 
present,  he  obtains  a  large  quantity  of  red  cuprous  oxide  after  two 
hours'  boiling,  which  increases  as  the  boiling  is  continued. 
Linz  therefore  concludes  "The  decomposition  of  the  alkali  and 
copper  tartrate,  by  strong  heating,  is  very  appreciable,  and  makes 
its  use  in  the  method  given  by  Tschirch  impossible.  Thereby 
Tschirch's  proposal  to  determine  glycyrrhizin  quantitatively  by  hy- 
drolysis with  Fehling  solution  falls  to  the  ground." 
Linz  then  shows  that  the  self-reduction  of  Fehling  solution  has 
already  been  known  in  the  literature,  that  it  must  be  serious  in  15 
hours  boiling,  that  the  degree  of  alkalinity  and  the  solution  volume 
also  affect  the  action  of  Fehling  solution,  and  that  there  is  a  tendency 
to  oxidation  as  well  as  reduction  during  15  hours  boiling.  (P.  A.  H.)] 
Linz  concludes : 
"I  will  summarize  my  objection  to  Tschirch's  idea  and  to  Erik- 
son's  procedure  as  follows : 
"The  proof  that  the  hydrolysis  of  glycyrrhizin  runs  quantita- 
tively is  not  attempted,  and  is  not  established. 
"On  the  contrary,  I  have  proved  that  a  quantitative  hydrolysis 
with  Fehling  solution  cannot  be  carried  out,  because  the  copper  or 
cuprous  oxide  weighed  is  derived  in  large  part  from  self-reduction 
of  the  Fehling  solution. 
"Before  the  actual  process  of  hydrolysis  begins,  appreciable 
quantities  are  lost,  of  the  substance  to  be  determined. 
"The  end  point  of  the  hydrolysis  cannot  be  sharply  established." 
