"^Vn^'i^o"™  }       Presence  of  Tannin  in  Gentian,  3 
a  member  of  the  present  class,  to  make  a  series  of  experiments  in  the 
laboratory  of  the  College,  and  he  has  complied  with  my  request  and 
carefully  examined  a  sample  of  the  same  root,  and  a  portion  of  the  con- 
centrated infusion,  preserved  by  the  addition  of  alcohol,  with  which  I 
experimented  about  four  years  ago.  He  also  procured  three  additionaf 
samples  of  gentian  root  of  good  and  fresh  appearance.  The  infusion 
had  deposited  a  precipitate  of  a  pectin  compound  ;  filtered  and  freed 
from  alcohol  by  evaporation,  the  liquid  gave  no  precipitate  with  gelatin. 
The  old  root  yielded  by  percolation  with  cold  water  a  rather  thick  and 
opaque  infusion,  which  produced  a  dark  greenish-black  color  with  ferric 
chloride,  and  a  gelatinous  precipitate  with  gelatin.  But  since  the 
infusion  could  not  be  obtained  perfectly  transparent  by  filtration,  and 
since  alum  solution  would  also  precipitate  it,  it  was  diluted  with  about 
an  equal  bulk  of  water,  and  on  standing  over  night  a  similar  gelatinous 
precipitate  of  pectin  had  separated,  and  the  clear  filtrate  was  not  pre- 
cipitated by  gelatin,  even  after  prolonged  standing,  and  yielded  only  a 
very  slight  coloration  on  the  addition  of  ferric  chloride.  A  dilute 
infusion  of  the  same  root  was  left  in  contact  for  over  a  week  with  a 
large  piece  of  fresh  hide,  when  ferric  chloride  produced  merely  a  slight 
tint  of  the  same  intensity  as  in  the  beginning  of  the  experiment. 
The  infusions  prepared  from  two  other  samples  of  root  were  not  dis- 
turbed by  gelat'in.  The  third  sample  apparently  yielded  a  slight  pre- 
cipitate with  gelatin  on  standing  ;  but  it  was  noticed  that  another  por- 
tion of  the  same  infusion,  to  which  no  gelatin  had  been  added,  likewise 
separated  a  precipitate  similar  in  amount  and  appearance  to  that  formed 
after  the  addition  of  the  gelatin,  and  evidently  consisting  of  a  pectin 
compound.  After  removing  this  spontaneous  precipitate  by  filtration, 
the  liquid  was  not  disturbed  by  gelatin,  tartar  emetic  or  sulphate  of 
cinchonidia. 
Since  it  was  found  impossible  to  procure  gentian  root,  the  clear  infu- 
sion of  which  would  give  a  decided  precipitate  with  gelatin,  further 
experiments  were  not  made  ;  but  Mr.  Baur  has  taken  steps  for  obtain- 
ing recently  dug  gentian  root  from  Europe  and  expects  to  continue  the 
investigation. 
From  the  observations  thus  far  made,  I  believe  it  is  safe  to  conclude 
that  commercial  gentian  root  is  free  from  tannin.  The  pectin  present 
in  the  root  is  doubtless  altered  in  the  course  of  time,  and  possibly  con- 
verted into  the  pectonic  acid  of  Fremy,  or  a  similar  compound,  which, 
while  not  entirely  insoluble  in  water,  becomes  so  in  the  presence  of 
