Am.  Jour.  Pharm. 
April,  1893. 
Cana igre  Tann in . 
167 
hydrogen  sulphide,  lead  sulphide  separated  by  filtration,  excess  of 
gas  boiled  out  of  filtrate,  the  last  made  alkaline  with  sodium  hydrate, 
and  heated  on  a  water-bath  with  Fehling's  solution  when  some 
reduction  occurred.  The  amount  of  cuprous  oxide  obtained  was 
less  than  that  obtained  from  the  -3  gram  used,  when  the  tannin 
extracted  by  commercial  ether  was  acted  on  with  the  same 
strength  hydrochloric  acid. 
The  evaporation  to  dryness  made  the  red  compound  more  insolu- 
ble in  water,  or,  by  removing  the  hydrochloric  acid,  entirely 
excluded  it  from  solution.  As  the  red  substance  was  found  to 
reduce  Fehling's  solution,  it  would  appear  probable  that  it  caused 
the  slight  reduction  observed. 
Red  Substance  Produced  by  Action  of  Acids, — This  was  washed 
thoroughly  with  absolute  ether  to  remove  crystalline  substances.  In 
mass  it  was  almost  black;  in  powder,  red-brown. 
It  was  partly  soluble  in  ammonium  hydrate,  sodium  hydrate, 
sodium  carbonate,  and  more  than  one-half  was  soluble  in 
alcohol.  The  part  soluble  in  alcohol  behaved  like  the  tannin 
toward  ferric  chloride.  This  was  also  the  portion  soluble  in 
alkalies.  Heated  with  Fehling's  solution,  the  latter  was  reduced. 
Cold  concentrated  nitric  acid  completely  oxidized  the  portion  soluble 
m  alcohol ;  hot  nitric  acid,  the  portion  insoluble  in  that  liquid. 
Upon  standing  in  contact  with  water  for  twenty-four  hours,  it  dis- 
solved only  to  an  extent  sufficient  to  color  the  water  reddish  yellow; 
the  residue  remaining,  as  before,  not  completely  soluble  in  alcohol. 
The  part  insoluble  in  alcohol  dissolved  sparingly  in  alkalies,  but 
only  upon  long  standing. 
Crystalline  Substance  Produced  by  Action  of  Acids. — The  colorless 
crystalline  substance,  removed  by  ether  previous  to  treatment  with 
Fehling's  solution,  gave  the  following  reactions  for  protocatechuic 
acid  : 
Ferric  chloride,    .  .  .  .  .  ^  green  color. 
Sodium  carbonate,  ....  J  red  color. 
Ferrous  sulphate,     ....  in  neutral  solution,  violet  color. 
Fehling's  solution,  ....  no  change. 
Ammoniacal  silver  nitrate,  reduced. 
Basic  lead  acetate,    ....  white  ppt. 
and 
white  ppt.,  nitrate  not  precipitated  by 
basic  lead  acetate  (absence  of  phloro- 
glucin). 
