2 
Presence  of  Tannin  in  Gentian. 
Am  Jour.  Pharro. 
Jan.,  1880. 
Mr.  Ville  concluded  that  the  gentisic  acid  is  the  tannin  of  gentian^  but 
he  failed  to  prove  that  the  aqueous  solution  of  this  acid  would  yield  a 
precipitate  with  gentian,  or  that  the  precipitate  by  gelatin  in  infusion  of 
gentian,  after  having  been  washed  with  cold  water,  would  be  affected 
by  ferric  chloride.  As  to  the  gradual  disappearance  of  the  dark  color- 
ation by  iron  salts  in  infusion  of  gentian  treated  with  fresh  hide,  I 
believe  that  this  may  be  easily  arrived  at  by  the  previous  removal  of 
pectin  compounds,  as  indicated  above,  to  such  an  extent  that  the  color 
of  the  infusion  will  be  scarcely  darkened  on  the  addition  of  the  iron 
salt,  owing  to  the  very  slight  solubility  of  the  coloring  principle,  gen- 
tisic acid,  in  cold  water. 
An  abstract  of  Mr.  Ville's  essay  will  be  found  in  the  "Year  Book 
of  Pharmacy,"  1877,  p.  217,  in  which  it  is  claimed,  that  "  he  obtained 
unmistakable  indications  of  the  presence  ot  tannin  with  ferric  chloride, 
gelatin  and  albumen,"  but  I  have  failed  to  find  in  the  essay  itself  any 
experiment  which  would  disprove  the  observations  made  by  myself  and 
Mr.  Patch  in  1876.  I  then  obtained  the  same  reactions  with  ferric  chlo- 
ride and  gelatin  as  Mr.  Ville,  but  showed  that  neither  was  due  to  tannin. 
At'"the  last  meeting  of  the  British  Pharmaceutical  Conference  a 
paper  was  read  by  Mr.  Edward  Davies  ("  Phar.  Jour,  and  Trans.," 
1879,  Sept.  20,  p.  220),  in  which  the  presence  of  a  trace  (o"o8  per 
cent.)  of  tannin  (pxohMy  gallotannic  acid)  in  recently  dried  gentian  root 
was  inferred  from  precipitates  obtained  in  the  infusion  by  gelatin,  acetate 
of  cinchonia  and  tartar  emetic,  and  from  the  distinct  darkening  of  color 
by  ferric  chloride.  Mr.  Davies  also  observed  that  the  infusion  of 
powdered  gentian  would  only  be  slightly  darkened  by  ferric  chloride, 
and  yield  a  faint  precipitate  with  gelatin  after  long  standing,  and  no  pre- 
cipitate with  tartar  emetic;  and  he  infers  that  this  trace  of  tannin  is 
liable  to  decomposition  when  the  root  is  powdered  and  so  exposed  to 
oxidation  ;  or  that  it  is  not  a  constant  constituent  of  gentian  root. 
It  will  be  observed  that  this  is  an  entirely  novel  view  of  the  question, 
differing  very  essentially  from  those  advanced  by  Mr.  Ville,  and  it  is  to 
be  regretted  that  Mr.  Davies  did  not  prove  his  position  completely, 
either  by  repeating  the  interesting  experiment  made  by  Mr.  Patch, 
alluded  to  above,  or  by  washing  the  gelatin  precipitate  and  afterwards 
ascertaining  the  effect  of  ferric  chloride  upon  it.  The  new  reactions 
brought  forward  embrace  tartar  emetic  and  the  salt  of  an  alkaloid. 
Desiring  to  examine  these  precipitates,  I  requested  Mr.  Chas.  Baur, 
