256 
ON  THE  ACIDS  AND  EESIN  OF  BENZOIN. 
wood.  The  altered  tannin  precipitated  on  cooling  in  beautiful 
red  flocks,  as  it  is  but  little  soluble  in  cold  water.  It  is  very  solu- 
ble in  alcohol,  and  its  solution  has  a  rich  scarlet  color,  which  is 
characteristic  of  this  species  of  tannin.  Its  alcoholic  solution, 
when  left  to  spontaneous  evaporation,  did  not  yield  crystals,  but 
formed  a  dark  resinous  mass.  The  clear  liquid  from  which  the 
red  flocks  were  precipitated,  when  neutralized  with  chalk,  gave 
no  indications  of  sugar.  Sugar,  however,  together  with  a  good 
deal  of  mucilage  and  resinous  matter,  with  some  larixinic  acid, 
is  contained  in  the  crude  decoction  of  larch-bark. 
Bark  of  the  common  black  Mangrove  (Rhizophora  Mangle  of 
botanists), — This  species  of  mangrove-bark  is  used  in  tanning, 
and  is  occasionally  imported  into  Great  Britain  for  this  purpose. 
It  has  a  brownish-red  color  :  the  color  of  its  decoction  is  the 
same.  The  tannin  it  contains  is  precipitated  from  its  solution 
both  by  acetate  of  lead  and  concentrated  sulphuric  acid.  When 
boiled  with  dilute  sulphuric  acid  no  sugar  is  produced,  and  the 
brownish-red  precipitate  which  falls  cannot  be  made  to  crystal- 
lize. 
In  conclusion,  I  would  observe  that  it  is  somewhat  remarkable 
that  so  many  of  the  tannins  which  give  bluish-black  precipitates 
with  persalts  of  iron  are  glucosides  ;  whereas  of  those  which  give 
olive-green  precipitates  with  persalts  of  iron,  so  far  as  I  know, 
only  one — to  wit,  the  tannin  of  the  willow — is  a  glucoside. — 
Lond.  Pharm.  Jour.,  Pec.  1861,  from  Proc.  Royal.  Soc. 
ON  THE  ACIDS  AND  RESIN  OF  BENZOIN. 
Since  Messrs.  Kolbe  &  Lauteman's  paper  on  the  acids  of  ben- 
zoin (see  page  220,  vol.  ix.  Am.  Jour.  Ph.)  announcing  the 
presence  in  the  benzoin  of  Sumatra,  of  toluylic  acid,  these 
chemists  by  new  researches  have  satisfied  themselves  that  the 
acid  in  question  is  not  that  acid,  but  a  compound  of  two  parts  of 
benzoic  and  one  part  of  cinnamic  acid. 
It  is  easy  to  be  assured  of  the  presence  of  this  last  acid  by 
boiling  the  benzoin  with  milk  of  lime,  filter,  precipitate  by  chlo- 
rohydric  acid,  and  add  permanganate  of  potassa.  If  cinnamic 
acid  is  present,  an  odour  of  oil  of  bitter  almonds  is  produced,  re- 
sulting from  the  reduction  of  that  acid. 
These  two  acids  are  always  met  with  in  the  same  proportions 
