654 
Chemistry  of  Gossypol. 
Am.  Jour.  Pharm. 
Sept.,  1918. 
If  little  free  fatty  acid  is  present  in  the  gossypol  extract,  the 
amount  of  gossypol  present  may  be  approximated  by  the  use  of 
standard  dilute  alkali.  Ether  and  other  fat  solvents  are  added,  if 
necessary,  to  destroy  emulsions.  Phenolphthalein  is  used  as  indi- 
cator. The  color  change  occurs  in  the  aqueous  layer  after  the  for- 
mation of  the  disodium  salt  of  gossypol. 
Method  3. — This  method  involves  the  use  of  aniline  as  a  pre- 
cipitating agent  for  gossypol.  A  very  slightly  soluble  compound,9 
apparently  the  dianiline  salt  of  gossypol,  is  formed,  which  separates 
out  of  an  oily  extract  on  standing  as  an  orange-yellow  micro- 
crystalline  precipitate.  Aniline  (about  5  per  cent,  of  the  weight  of 
the  extract)  is  added  to  an  ether  extract  of  cottonseed.  The  mix- 
ture is  warmed  on  the  water  bath  and  set  aside  to  stand  a  week  or 
more.  If  given  sufficient  time  the  yield  is  practically  quantitative 
and  the  method  has  been  used  to  estimate10  the  amount  of  gossypol 
in  extracts  of  cottonseed  products. 
The  aniline-gossypol  compound  is  filtered  out  and  washed  free 
from  oil,  etc.,  with  ether,  or  with  a  small  amount  of  ether  followed 
by  larger  amounts  of  petroleum  ether.  It  may  be  purified  by  re- 
crystallization  from  aniline. 
To  prepare  gossypol  from  the  aniline  compound  it  is  dissolved 
in  hot  alcoholic  potash  to  decompose  it  and  the  aniline  is  steam- 
distilled  out.  The  resultant  aqueous  solution  of  potassium  "gos- 
sypolate  "  is  treated  with  a  pinch  of  sodium  hyposulphite  (Na2S204) 
in  order  to  reduce  any  of  the  blue  oxidation  product  which  may  be 
formed.  The  gossypol  is  then  precipitated  in  amorphous  flocks  by 
acidifying.  It  may  be  filtered  out  or  removed  from  the  solution  by 
shaking  with  ether  in  a  separatory  funnel.  It  may  be  purified  ac- 
cording to  Method  1. 
Molecular  Weight  of  Gossypol. — It  was  first  sought  to  deter- 
mine the  molecular  weight  of  gossypol  by  physical  methods.  Prepa- 
rations of  gossypol  recrystallized  from  alcohol  with  the  addition  of 
50  per  cent,  acetic  acid  were  first  used.  The  results  with  various 
solvents  were  not  uniform.  Thus,  while  the  boiling-point  method 
with  ether  and  acetone  indicated  a  molecular  weight  of  300  to  350; 
with  alcohol,  benzene  and  carbon  tetrachloride, "  the  elevation  of  the 
9  This  compound  was  discovered  by  Dr.  J.  T.  Dobbins  working  in  this 
laboratory  in  attempts  to  prepare  "  B  "  gossypol. 
10  This  method  therefore  may  be  used  to  approximate  the  relative  tox- 
icity of  extracts.    (See  /.  Biol.  Chem.,  32,  87  (1917).) 
