ON  CATECHU  AND  ITS  ACIDS. 
331 
separated  by  sulphuric  acid;  the  solution  was  tested  for  sugar, 
but  not  a  trace  was  found.  The  above  cinnamon-colored  matter 
was  insoluble  in  water,  alcohol  and  ether,  caustic  potassa  was 
colored  slightly  violet  by  it,  concentrated  sulphuric  acid  dissolved 
it,  which  solution  was  precipitated  by  water. 
The  behaviour  of  catechu-tannin  to  sulphuric  acid  was  tried 
in  a  similar  manner.  Bombay  catechu  was  exhausted  with  ether, 
the  solution  treated  with  water  and  evaporated  to  dryness ;  the 
residue  dissolved  in  water  and  filtered  from  the  crystallized  cate- 
chuic  acid.  After  long  standing,  the  filtrate  separated  only  some 
brown  matter,  but  no  catechuic  acid  ;  it  was  precipitated  with 
and  washed  with  sulphuric  acid,  and  after  pressing  several  hours, 
boiled  with  diluted  sulphuric  acid.  The  reaction  and  subsequent 
treatment  was  the  same  as  above  ;  5  C.  0.  of  Fehling's  test  sepa- 
rated only  traces  of  suboxide  of  copper.  Analysis  showed  the 
cinnamon-colored  matter  to  consists  of  C17  H1()  Oi0 ;  but  there 
was  no  proof  of  its  purity.  The  purest  catechuic  acid  reduces 
suboxide  of  copper  from  Fehling's  test  liquid. 
From  the  above  the  author  comes  to  the  following  conclusions  : 
1.  Pure  cateclm-tannic  acid  cannot  be  obtained  by  any  of  the 
above  methods. 
2.  Catechuic  acid  bears  not  the  same  relation  to  catechu-tan- 
nxn  as  gallic  acid  to  gallo-tannin. 
3.  The  different  properties  of  the  different  kinds  of  catechu 
are  probably  the  result  of  a  different  process  of  preparation.* 
4.  The  catechuic  acid  of  the  different  kinds  of  catechu  is  the 
same  ;  composition  C17  H12  Q10,  of  which  3H0  are  expelled  at 
100°  C.  (212°  F.) 
5.  Catechuic  acid  is  decomposed  if  exposed  to  a  heat  of  100° 
C.  for  a  long  time. 
6.  Pure  catechuic  acid,  decomposed  by  sulphuric  acid,  yields 
much  of  a  brown  insoluble  substance,  but  no  sugar. 
*  Nees  von  Esenbeck  says,  in  Buehner's  Report,  xliii.,  352 : 
"  As  Bombay  catechu  contains  though  less  catechin,.  we  return  to  our 
opinion  that,  like  gambir,  it  is  obtained  from  Uncaria  gambir.  Its  smaller 
amount  of  catechin,  its  larger  of  tannin  and  its  browner  color,  may  be 
due  to  the  boiling  of  the  branches  and  the  wood  of  the  Uncaria  and  the 
subsequent  evaporation.  It  is  also  not  impossible  that  the  branches  from 
which  the  gambir  has  been  prepared,  by  decoction  yield  an  extract  resem- 
bling Bombay  catechu." 
