AN  ESSAY  ON  SENNA. 
195 
no  precipitate,  indicating  the  probable  presence  of  "  Gallic 
Acid."  A  solution  of  basic  acetate  of  lead  was  added  to  the 
infusion  as  long  as  a  precipitate  was  produced.  This  was  of  a 
dirty  yellow  color,  and  was  collected  on  a  filter.  The  excess  of 
lead  was  removed  from  the  filtrate  by  the  cautious  addition  of 
sulphuric  acid.  After  filtration  from  the  precipitated  PbO,S03, 
the  liquid  was  of  a  pale  straw  color,  and  possessed  a  rather 
agreeably  sweet  odor  and  taste.  It  was  evaporated  to  a  small 
bulk,  when  there  were  deposited  in  the  capsule,  small,  distinct 
yellowish  crystals,  seemingly  insoluble  in  water,  alcohol  or  ether, 
but  were  rendered  white  by  agitation  with  these  liquids.  At  the 
intimation  of  Prof.  Procter  of  the  possibility  of  this  product 
being  CaO,S03,  some  of  the  crystals  were  agitated  with  distilled 
water ;  to  a  part  was  added  a  solution  of  oxalate  of  ammonia, 
and  the  remainder  was  treated  with  a  solution  of  nitrate  of 
baryta.  Both  these  reagents  afforded  the  characteristic  reactions 
of  lime  and  sulphuric  acid,  the  base  having  pre-existed  in  the  senna 
leaves,  and  the  acid  resulting  from  the  removal  of  the  lead  in  the 
process  gone  over.  The  solution  was  farther  evaporated,  by  a 
gentle  heat,  to  an  extractive  mass,  having  an  exceedingly  sweet, 
and  at  the  same  time  nauseous  taste. 
Suspecting  the  presence  of  a  variety  of  grape  sugar,  a  small 
portion  was  subjected  to  Trommer's  test,  which  gave  immediate 
evidence  of  glucose.  There  was  apparent  also  in  the  extract  a 
notable  proportion  of  lime.  Twenty  grains  taken  in  aqueous 
solution  produced  no  cathartic  effects  upon  the  bowels. 
Exp.  II.  To  find  the  percentage  of  CaO,  existing  in  the  drug, 
two  troyounces  of  the  leaves  were  exposed  to  a  full  red  heat  in  a 
crucible.  The  resulting  mass  of  ashes  was  exhausted  of  inor- 
ganic salts  by  water,  acidulated  with  muriatic  acid.  The  lime  was 
precipitated  as  oxalate,  by  oxalate  of  ammonia.  The  oxalate  of 
lime  was  collected  and  heated  in  a  porcelain  crucible  until 
the  vegetable  acid  was  sufficiently  decomposed.  The  resulting 
mixture  of  CaO  and  CaO,C02,  was  repeatedly  treated  with  a  solu- 
tion of  carbonate  of  ammonia,  heated  and  weighed,  until  the 
farther  addition  of  the  carbonate  produced  no  increase  in  weight. 
The  CaO,C02  thus  produced  weighed  52  grains,  containing, 
therefore,  about  29  grains  of  CaO,  showing  the  per  cent,  of  lime 
in  senna  to  be  3-03. 
