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ON  SOME  VARIETIES  OF  TANNIN. 
each  specimen  until  it  ceases  to  have  any  dilating  effect,  and 
then  see  which  has  borne  dilution  best. 
Finally,  the  new  view  runs  counter  to  very  old  opinions  ex- 
pressed and  acted  on  by  writers  and  the  general  public  in  all 
ages,  that  the  dark  livid-green  of  certain  plants  points  to  their 
poisonous  properties  ;  an  opinion  expressed  by  Pereira,  who  re- 
fers to  the  "  dark  lurid  aspect  of  the  Belladonna  plant,  as  indic- 
ative of  its  deadly  narcotic  quality." — London  Pharm.  Jour. 
Jan.  1862. 
ON   SOME   VAKIETIES  OF  TANNIN. 
By  John  Stenhouse,  LLD.,  F.  R.  S.f  F.  C.  S. 
In  two  communications  "  On  some  Astringent  Substances  as 
sources  of  Pyrogallic  Acid,"  read  before  the  London  Chemical 
Society  in  the  years  1842,  1843,  I  showed  that  the  usual  division 
of  the  varieties  of  tannin  into  two  genera — to  wit,  those  which 
give  black,  and  those  which  give  green  precipitates  with  salts  of 
iron — though  called  in  question  by  Berzelius,  is  still  well  founded : 
and  likewise,  that  these  two  genera  consist  of  a  great  variety  of 
species,  which,  though  closely  resembling  each  other  in  proper- 
ties, are  still  dissimilar  in  nature  :  the  only  instance  in  which 
the  same  species  of  tannin  had  been  procured  from  two  different 
plants,  being  those  of  nut-galls  and  sumach.  Professor  Strecker's 
important  observation  made  some  seven  years  ago,  that  grape- 
sugar  is  produced  when  the  tannin  of  nut-galls  is  boiled  with  di- 
lute sulphuric  acid,  seemed  to  render  a  further  examination  of 
the  varieties  of  tannin  desirable. 
Sumach, 
As  the  tannin  of  sumach  cannot  be  obtained  in  such  a  high 
state  of  purity  as  that  of  nut-galls  by  Pelouze's  ether  process,  I 
was  obliged  to  employ  other  methods  by  no  means  so  satisfactory, 
but  which  still  yield  a  tolerably  pure  tannin.  A  strong  decoc- 
tion of  sumach  was  therefore  treated  with  acetate  of  lead,  which 
threw  down  a  pale  yellow  precipitate.  This  was  washed  by  de- 
cantation,  and  then  decomposed  by  sulphuretted  hydrogen  and 
filtered  ;  the  filtrate  having  been  boiled  with  dilute  sulphuric  acid, 
on  standing  for  some  time,  deposited  crystals  of  impure  gallic 
acid.    These  were  collected  on  a  filter,  and  the  mother-liquor, 
