49°  Estimation  of  Tannin  in  Hops.  {Amoctuyi89iarm* 
there  is  slight  fulness  of  the  vessels,  and  swelling  of  the  mucous 
membrane.  In  the  urine  a  trace  of  albumen  is  sometimes  found, 
and  at  times  there  is  a  constituent  present  which  is  capable  of 
reducing  copper. 
Poulsson  says  that  filicin  does  not  give  rise  to  symptoms  of  poi- 
soning even  in  doses  of  I  grm.  to  iy2  grm.  Occasionally  a  little 
diarrhoea  occurs,  perhaps  owing  to  a  little  filicic  acid  being  formed. 
Its  inertness  is,  perhaps,  due  to  its  insolubility.  If  given  with 
alkalies  it  is  converted  into  the  active  filicic  acid. 
Filicic  acid  is  soluble  in  the  intestinal  contents,  but  with  difficulty 
absorbed,  hence  it  kills  and  drives  out  parasites  without  injuring  the 
organism.  Poulsson's  experiments  seem  to  show  that  it  is  the 
essential  active  principle,  and  it  seems  probable  that  we  may  be 
able  to  employ  filicic  acid  instead  of  the  extract,  a  manifest  advan- 
tage, because  it  is  not  disagreeable  whilst  the  extract  is  very 
nauseous. 
ESTIMATION  OF  TANNIN  IN  HOPS.1 
By  E.  Kokosinsk. 
The  method  depends  on  the  property  of  tannin  of  absorbing 
iodine  in  presence  of  alkaline  carbonates.  • 
The  solution  is  prepared  by  boiling  10  grams  of  hops,  the  solution 
being  diluted  to  500  cc.  If  the  hops  have  been  sulphured,  a  few 
drops  of  hydrogen  peroxide  are  added  to  the  water  before  commenc- 
ing to  boil.  The  extract  is  filtered  from  the  hops.  The  solutions 
required  are  :  (1)  normal  solution  of  sodium  carbonate  ;  (2)  normal 
sulphuric  acid  ;  (3)  N.  iodine  ;  (4)  N.  solution  of  sodium. thio- 
sulphate  9920  gram  in  I  litre;  (5)  a  solution  of  pure  tannin  pre- 
pared from  galls  which  contains  0-05  gram  tannin  in  100  cc;  (6)  a 
freshly  prepared  solution  of  starch. 
Three  flasks  of  about  100  cc.  capacity  are  employed;  into  the 
first  is  put  10  cc.  of  water,  into  the  second  10  cc.  of  the  tannin 
solution,  into  the  third  10  cc.  of  the  hop  extract.  To  each  flask  4  cc. 
of  the  normal  sodium  carbonate  solution  is  added,  and  immediately 
afterwards  20  cc.  of  the  standard  iodine  solution.  Flasks  2  and  3 
are  then  tested  for  free  iodine  by  placing  a  drop  of  the  solution  on 
a  piece  of  starch  paper,  and  if  free  iodine  is  not  present,  more  of 
1  Chem.  Centr.,  1891,1,  377  ;  Jour.  Chem.  Society,  July,  p.  870. 
