268    Chemical  Examination  of  Ipomosa  Purpurea.  {Amjine?i908?rm* 
V.  Alcohol  Extract  of  the  Resin. 
This  constituted  by  far  the  largest  proportion  of  the  total  resin, 
and,  when  dry,  could  readily  be  reduced  to  a  very  light  brown,  mo- 
bile powder. 
In  order  to  insure  the  freedom  of  this  resin  from  substances  sol- 
uble in  water,  it  was  dissolved  in  alcohol  and  reprecipitated  by  the 
addition  of  water.  Its  further  purification  was  effected  by  heating 
the  alcoholic  solution  with  a  little  pure  animal  charcoal.  After  fil- 
tering the  liquid  and  removing  the  solvent  a  very  light  colored  prod- 
uct was  obtained,  which,  when  dry,  could  be  reduced  to  a  perfectly 
white  powder. 
The  resin,  purified  as  above  described,  after  being  dried  at  1 10°  C. 
was  found  to  soften  at  1400  C,  and  to  melt  somewhat  indefinitely 
between  150  and  1600  C.  When  heated  on  platinum-foil  it  fuses, 
chars,  and  burns  with  a  smoky  flame,  leaving  finally  no  visible  resi- 
due. With  cold,,  concentrated  sulphuric  acid  it  gives  only  a  light 
brown  color,  whereas  with  nitric  acid  no  coloration  is  produced. 
The  optical  rotatory  power  of  this  purified  resin  was  determined 
in  the  same  manner  as  has  been  described  in  connection  with  the 
crude  resin.  An  alcoholic  solution  containing  1  3070  gramme  of  the 
resin  in  25  c.c.  had  an  initial  rotation  of  —  27°  in  a  I  dcm.  tube, 
whence  [a]D  —  51-64°. 
With  the  endeavor  to  ascertain  whether  this  resin  is  homogeneous 
in  character,  10  grammes  of  it  were  dissolved  in  100  c.c.  of  alcohol, 
and  to  this  solution  was  added  an  alcoholic  solution  of  lead  acetate. 
As  no  precipitate  was  produced,  an  alcoholic  solution  of  ammonia 
was  subsequently  added  in  slight  excess,  when  an  abundant  precipi- 
tate was  obtained.  This  precipitate  was  collected,  well  washed  with 
alcohol,  then  suspended  in  alcohol,  and  decomposed  by  hydrogen 
sulphide.  After  the  removal  of  the  lead  sulphide  by  filtration,  the 
liquid  was  concentrated  to  a  small  bulk,  and  ether  added  to  precipi- 
tate the  resin,  which  was  subsequently  dissolved  in  a  little  alcohol, 
the  solution  evaporated,  and  the  residue  dried.  The  weight  of  the 
resin  which  had  thus  been  precipitated  by  the  basic  lead  acetate 
was  6  grammes.  The  alcoholic  filtrate  from  the  basic  lead  acetate 
precipitate  was  deprived  of  lead  by  means  of  hydrogen  sulphide, 
and,  after  filtration,  concentrated  to  the  consistency  of  a  syrup.  On 
the  subsequent  addition  of  ether  a  quantity  of  resin  was  precipitated, 
