ON  SOME  VARIETIES  OP  TANNIN. 
253 
when  neutralized  with  chalk,  gave  abundant  indications  of  sugar, 
both  by  Trommer's  test  and  when  subjected  to  fermentation.  A 
second  decoction  of  sumach,  when  cold,  was  treated  with  sul- 
phuric acid,  which  threw  down  a  copious  precipitate  :  this,  when 
boiled,  was  also  resolved  into  gallic  acid  and  grape-sugar.  This 
reaction,  therefore,  in  addition  to  former  experiments,  serves  to 
confirm  the  identity  of  tannin  in  oak-galls  and  sumach. 
When  sumach  is  long  kept,  the  tannin  it  contains  appears  to 
be  resolved,  in  a  great  measure,  into  gallic  acid  and  grape-sugar, 
owing  to  its  undergoing  a  species  of  natural  fermentation.  Ac- 
cordingly, under  these  circumstances,  when  simply  boiled  with 
water,  sumach  emits  an  odor  resembling  that  of  tea,  and  yields 
a  large  quantity  of  sugar  and  gallic  acid,  but  mixed  with  much 
impurity.  Sumach,  therefore,  though  it  contains  much  gallic 
acid,  owing  to  the  impurities  present  in  it,  is  not  a  good  source 
of  that  acid. 
I  may  also  remark,  that  the  amount  of  tannin  in  sumach  varies 
considerably,  some  specimens  being  very  rich  and  others  very 
poor.  This  probably  arises  from  the  circumstance  that  the  su- 
mach of  commerce  is  the  product  of  various  kinds  of  Rhus,  such 
as  Rhus  cotinus,  Rhus  coriaria,  &c. 
Chinese  G-alls. 
These  singularly-shaped  galls,  which  are  angular  and  slightly 
translucent,  have  been  imported  into  this  country  in  small  quan- 
tities for  the  last  fourteen  or  fifteen  years.  They  are  said  to  be 
found  on  the  branches  of  a  plant  which  grows  in  Japan.  From 
the  small  amount  of  the  coloring  matter  they  contain,  Chinese 
galls  are  greatly  preferred  for  the  manufacture  of  gallic  acid. 
Oak-galls,  on  the  other  hand,  are  the  best  source  of  pyrogallic 
acid.  The  decoction  of  Chinese  galls  gave  a  copious  white  pre- 
cipitate with  acetate  of  lead.  This  was  decomposed  by  sulphu- 
retted hydrogen,  and  filtered  ;  the  clear  liquid,  when  boiled  with 
sulphuric  acid,  was  resolved  into  gallic  acid  and  grape-sugar,  as 
in  the  two  preceding  instances.  Another  portion  of  the  filtered 
liquid  was  evaporated  to  dryness,  and  destructively  distilled.  It 
yielded  a  very  large  quantity  of  pyrogallic  acid.  It  is  clear, 
therefore,  that  gall  nuts,  Chinese  galls,  and  the  various  kinds  of 
sumach,  contain  the  same  species  of  tannin. 
