ADeimbe?bil97m }    Recent  Literature  Relating  to  Pharmacy.  641 
The  osazone  of  caffetannic  acid,  QgH^NgO^  crystallizes  in  yellow 
needles,  very  sparingly  soluble  in  alcohol,  and  melts  at  1800  ;  it  is 
insoluble  in  most  media,  and  is  so  sparingly  soluble  in  phenol  and 
naphthalene  that  no  determinations  of  molecular  weight  have  been 
possible. 
The  sugar,  C6H1206,  obtained  on  hydrolyzing  caffetannic  acid,  will 
be  described  in  a  subsequent  paper. — Journal  of  the  Chemical 
Society,  London,  October,  1897. 
PREPARATION  OF  HYDROGEN  PEROXIDE. 
Hydrogen  peroxide  may  rapidly  and  economically  be  prepared, 
according  to  Pedro  Etchegorry  (Tribuna  Farmaceutico,  i,  16),  by 
triturating  with  ice  a  mixture  of  1  part  barium  peroxide  and  2  parts 
(by  weight)  of  hydrochloric  acid.  The  following  reaction  takes 
place. 
BaOa  \  2HCI  ==  H202  -f  BaCl2. 
The  filtered  solution  is  treated  with  a  solution  of  silver  sulphate 
until  no  more  precipitation  occurs,  according  to  the  following 
reaction : 
BaCl2  +  H202  +  Ag2S04  =  BaSO,  +  2AgCl  -f  H202. 
On  filtering,  the  barium  sulphate  and  silver  chloride  are  retained 
on  the  filter,  while  the  hydrogen  peroxide  passes  into  the  filtrate  in 
a  state  of  purity. 
This  process  has  already  appeared  in  some  text-books  on  chemistry* 
and,  consequently,  is  not  new;  but  it  seems  worthy  of  further 
investigation. 
CAFFETANNIC    ACID  (GLUCOSYLCAFFEIC  ACID)    AND   ITS  DECOMPOSITION 
INTO  CAFFEIC  ACID,  VINYLCATECHOL,  AND  CATECHOL. 
Hermann  Kunz-Krause  [Ber.y  1897,  30,  1617-1622)  has  recently 
studied  this  subject.  Both  caffetannic  acid  and  matetannic  acid, 
when  hydrolized,  yield  a  syrupy  sugar  and  caffeic  acid  (dihydroxy- 
cinnamic  acid).  This  acid,  when  heated  at  200°,  readily  loses 
carbonic  anhydride,  yielding  vinylcatechol  (3 :  4-dihydroxycinna- 
mene),  the  decomposition  at  this  temperature  being  quantitative. 
A  characteristic  reaction  for  vinylcatechol  is  the  one  previously 
mentioned  [Arch.  Pharm.,  1893,  231,  635).  This  reaction  is  also 
given  by  Tiemann  and  Will's  hesperetol  or  vinylcatechol  paramo- 
