478  Chemical  and  Pharmacognostical  Notes.      <  Am'Sepl!1 iS*""' 
German  method  of  separating  digitalin  from  the  other  compounds 
occurring  in  Digitalis  purpurea  is  based  on  the  precipitation  of  the 
former  by  means  of  tannin ;  the  French  method  on  the  insolubility  of 
digitalin  and  digitin  in  water,  digitalein  being  readily  soluble. 
Both  methods  are  troublesome  and  demand  much  time.  R.  Palm 
("Anal.  Zeitschr.  [23],  pp.  22,  23)  extracts  the  powdered  herb  with 
water,  filters  the  solution  through  animal  charcoal  until  it  is  colorless, 
and  precipitates  the  organic  acids  with  neutral  plumbic  acetate.  A  solu- 
tion of  lead  acetate  and  alcoholic  ammonia  is  then  added  to  the  filtrate 
as  long  as  a  precipitate  is  produced.  This  contains  all  the  principles 
and  is  washed  with  water,  and  decomposed  with  hydrogen  sulphide. 
The  solution,  separated  from  the  precipitate,  contains  all  the  digitalein, 
the  precipitate  consisting  of  plumbic  sulphide,  digitalin  and  digitin. 
The  digitalin  is  extracted  from  the  dried  residue  by  chloroform,  and 
digitin  with  alcohol. 
Action  of  Bromine  on  pilocarpine. — (Chastaing,  Comp.  Rend.  [97],  pp. 
1435-1437.)  When  bromine  is  added  to  a  solution  of  pilocarpine  in 
chloroform,  there  is  development  of  heat,  the  mixture  becomes  acid? 
and  a  heavy  oily  liquid  separates.  The  supernatant  chloroform  retains 
the  excess  of  bromine  together  with  a  small  quantity  of  the  bromo- 
derivative,  which  gradually  crystallizes  out.  The  oily  liquid  is  rapidly 
evaporated,  and  forms  a  deep  golden-yellow  resinous  mass,  which  is 
then  dissolved  in  chloroform,  from  which  it  separates  in  a  mass  of 
minute  prismatic  crystals.  These  crystals  have  the  composition 
Cj^jgN^jOgBr,,  and  consist  of  a  dibromide  of  dibromopilo  car  pine 
hydrobromide,  CnHuBr2N202HBr,  Br2.  This  substance  is  inodorous, 
but  when  exposed  to  air  it  absorbs  moisture  and  gives  off  ethyl  bromide, 
undergoing  some  alteration  which  results  in  the  formation  of  a  com- 
pound containing  less  carbon  than  the  original  substance.  In  contact 
with  copper,  dibromide  of  dibromopilocarpine  hydrobromide  gives  up 
part  of  its  bromine,  and  when  treated  with  silver  oxide  in  presence  of 
water  and  chloroform,  it  loses  Br3  and  yields  dibromopilocarpine, 
CnH14Br2N202,  which  resembles  pilocarpine  in  appearance,  but  is  less 
mobile  and  less  strongly  alkaline ;  it  is  precipitated  by  platinum 
chloride. 
The  action  of  bromine  on  pilocarpine  in  presence  of  a  small  quantity 
of  water  does  not  yield  dibromide  of  dibromopilocarpine  hydrobromide, 
but  the  corresponding  derivative  of  a  feebler  base  which  contains  an 
atom  of  carbon  less  than  pilocarpine.    This  carbon  is  given  off  as  car- 
