398  Glycyrrhizin  in  Licorice  Root.        j  Amju°er issi*""' 
If  then  the  quantitative  solubility  values  seem  to  have  no 
value,  it  becomes  all  the  more  important  to  establish  the  following 
facts : 
Glycyrrhizic  acid  is  only  very  slightly  soluble  in  water,  and  less 
so  in  water  of  o°  than  at  1 5°. 
Glycyrrhizic  acid  is  also  somewhat  soluble  in  acidified  water, 
but  noticeably  less  so  than  in  pure  water. 
j.  Experiments  to  Establish  Quantitatively  the  Losses  Caused 
by  the  Solubility  of  Glycyrrhizic  Acid. — The  only  procedure  which 
has  up  to  now  attempted  to  establish  in  a  glycyrrhizin  determination, 
the  losses  due  to  solubility,  and  to  give  a  figure  for  them  is  that  of 
Cornimboeuf .  I  will  discuss  it  at  this  place  since  Cornimboeuf  only 
treats  of  the  estimation  of  glycyrrhizic  acid  in  ammoniated  glycyr- 
rhizin, which  is  not  the  purpose  of  this  work.  Cornimboeuf  filters 
the  glycyrrhizin  which  has  been  precipitated  with  sulphuric  acid,  and 
dissolves  it  in  ammonia.  He  evaporates  the  supernatant  liquid,  to- 
gether with  the  wash  waters  almost  to  dryness,  kneads  the  tough 
black  residue  successively  with  10,  10,  and  5  cc.  of  water,  filters  the 
wash  water,  dissolves  the  remaining  second  portion  of  glycyrrhizic 
acid  in  ammonia,  unites  the  two  ammoniacal  glycyrrhizic  solutions 
and  drys  them  to  constant  weight.  I  do  not  consider  this  procedure 
free  from  objection. 
Independently  of  Cornimboeuf,  but  in  a  similar  way,  I  have 
often  attempted  to  determine  at  least  approximately,  the  quantitative 
losses  of  glycyrrhizin,  but  I  always  made  the  same  observation.  As 
the  evaporation  of  the  mother  liquid  and  the  wash  waters  prog- 
ressed, the  glycyrrhizic  acid  separated  out  at  first  in  brown  flakes, 
which  in  the  course  of  further  evaporation  became  deep  black.  They 
proved  to  be  very  difficultly  soluble,  and  partly  quite  insoluble  in 
ammonia.  When  one  remembers  that  during  evaporation,  the  water 
is  volatilized,  but  not  the  sulphuric  acid  used  for  precipitation,  and 
that  at  the  end  the  glycyrrhizin  in  the  mixture  is  in  solution  in  a 
very  strong  sulphuric  acid,  one  has  a  sufficient  explanation  for  this 
condition.  Under  the  influence  of  the  strong  acid,  decomposition 
has  taken  place,  and  partial  carbonization  will  occur,  especially  when 
the  evaporation  is  carried  almost  to  dryness  according  to  Cornim- 
boeuf's  method. 
Naturally  the  kneading  of  the  sticky  acid  with  25  cc.  water 
also  causes  losses,  but  unfortunately  such  losses  cannot  be  avoided  in 
the  glycyrrhizin  determination. 
