A\i°y^',i873RM  }   Gleanings  from  the  European  Journals.  22% 
vessel,  evaporating  the  dialyzed  portion  and  taking  up  by  ether ;  2,  by 
drying  it  for  several  months  over  sulphuric  acid,  taking  up  with  anhy- 
drous ether,  agitating  the  solution  with  water  and  evaporating  the 
lower  stratum ;  3,  by  dissolving  it  in  a  mixture  of  equal  volumes  of 
water  and  saturated  table-salt  solution,  saturating  the  liquid  with 
pure  table-salt,  treating  the  precipitate  in  the  same  mariner,  then  dis- 
solving it  in  dilute  solution  of  table-salt,  and  extracting  the  pure  tan- 
nin by  acetic  ether. 
The  resulting  dense  white  or  yellowish  powder,  which  had  been 
dried  at  120°  C.  (248°  F.),  yielded,  by  ultimate  analysis,  results 
which  closely  agreed  with  the  composition  of  gallic  acid  (C28H12O20)y 
minus  20.  Gallotannic  acid  may,  however,  be  converted  into  gallic 
acid  in  an  atmosphere  entirely  devoid  of  oxygen  ;  the  latter  cannot, 
therefore,  be  a  product  of  oxidation  of  the  former.  On  exposing 
pure  tannin  for  several  hours  in  an  air-bath  to  a  temperature  of  140 
—145°  C.  (284—293°  F.),  a  loss  in  weight,  due  to  expelled  water, 
was  observed,  and  the  residue  agreed  better  with  the  formula  given 
by  Mulder,  C^H^O^.  This  appears  to  be  the  correct  empirical  for- 
mula;  the  tannin,  however,  even  when  dried  at  120°  C,  persistently 
retains  a  little  water. 
That  tannin  is  not  merely  the  anhydride  of  gallic  acid,  but  that  on 
conversion  into  the  latter  the  grouping  of  the  elements  must  be 
changed,  is  proven  by  the  action  of  concentrated  sulphuric  acid  upon 
the  two  compounds  at  the  temperature  of  the  water-bath.  Gallic  acid 
yields  under  these  conditions  rufigallic  acid,  while  gallotannic  acid 
gives,  under  the  evolution  of  much  sulphurous  acid,  a  brown  amorphous 
product  which  is  not  related  to  rufigallic  acid. 
An  aqueous  solution  of  pure  tannin  is  not  affected  by  exposure  to 
the  light,  if  the  atmosphere  be  excluded. — Zeitschr.  f  AnaL  Chemie*. 
1872,  xi,  365—381. 
Estimation  of  Alcohol  in  Chloroform.  Dr.  A.  C.  Oudemans,  Jr., 
recommends  to  agitate  in  a  flask  7  to  10  c.c.  of  the  chloroform  at  & 
temperature  of  17°  C.  (62*G°  F.)  with  an  excess  of  dry  cinchonia. 
After  an  hour  the  liquid  is  filtered,  the  funnel  being  kept  covered 
with  glass,  and  5  c.c.  of  the  filtrate  are  evaporated  in  a  tared  capsule. 
From  the  weight  of  the  dissolved  cinchonia  the  alcohol  may  be  esti- 
mated by  the  following  table,  in  which  the  alcohol  is  given  in  per  cent,, 
by  weight,  and  the  solution  (5  c.c.)  measured  at  17°  C.  : 
