394 
Notes  on  the  Tannins. 
A.m.  Tour.  Pharrri, 
Aug.,  1878. 
Cutch  of  commerce  is  a  hard,  brownish-black,  shining  substance, 
prepared  in  India  and  elsewhere  from  the  Acacia  Catechu,  and  other 
trees. 
The  method  of  procedure  employed  in  our  experiments  consisted  in 
boiling  cutch  for  a  number  of  hours  with  a  quantity  of  dilute  sulphuric 
acid  (2 — 5  per  cent.)  During  this  operation  5  per  cent,  of  a  dark 
brown  insoluble  matter  forms,  which  appears  to  be  an  imperfectly 
changed  substance,  judging  from  its  general  characters  and  from  the 
fact  that  it  gives  the  reactions  of  a  glucoside,  only  in  a  less  degree  than 
the  original  cutch.  The  sulphuric  acid  solution  admits  of  treatment 
in  two  ways.  It  may  be  precipitated  either  by  acetate  of  lead  or  by 
baryta-water,  both  of  which  reagents  remove  the  same  acid  substance* 
and  leave  glucose  of  an  unfermentable  character  in  the  filtrate.  This 
glucose  was  estimated  at  25  per  cent,  on  the  original  cutch. 
Mimosa  bark  is  the  product  of  the  Acacia  mimosa,  and  furnishes  in 
part  the  cutch  of  commerce.  Extracts  made  of  this  bark  gave,  by  the 
processes  just  described,  similar  results,  the  sugar  obtained  being  esti- 
mated at  about  8  per  cent,  on  the  bark. 
The  peculiar  acid  removed  by  precipitation  with  acetate  of  lead  or 
baryta-water  deserves  a  few  words.  If  lead  be  employed,  the  acid  may 
be  obtained  by  decomposition  of  the  precipitate  with  sulphuretted 
hydrogen,  and  removal  of  the  sulphuric  acid  from  the  concentrated 
filtrate  by  means  of  carbonate  of  barium  or  carbonate  of  lead. 
If  baryta-water  be  employed,  it  is  best  to  decompose  the  precipitate 
with  sulphuric  acid,  and  then  to  remove  the  excess  of  acid  from  the 
filtrate  in  the  same  way. 
The  solution  of  organic  acid  thus  obtained  is  of  a  faint  red  color* 
and  shows  the  following  reactions  : 
1.  An  intensified  red  color  on  addition  of  ammonia. 
2.  A  dark  color  with  ferric  chloride,  but  only  a  trace  of  precipitate. 
3.  No  appreciable  reaction  with  ferrous  sulphate. 
But  a  solution  rendered  neutral  with  soda  became  much  darker 
itself,  and  gave 
1.  With  ferric  chloride  a  dark-colored  precipitate. 
2.  With  ferrous  sulphate  a  bluish-black  precipitate. 
It  also  gave  precipitates  with  other  reagents. 
On  evaporating  a  solution  of  the  free  acid,  oxygen  was  evidently 
absorbed,  and  a  dark-brown  matter  deposited  on  the  sides  of  the  dish. 
