THE 
AMERICAN  JOURNAL  OF  PHARMACY. 
MAY,  1  869. 
QUANTITATIVE  DETERMINATION  OF  THE  AMOUNT  OP 
TANNIN  IN  VARIOUS  YEGETABLE  ASTRINGENTS. 
By  Henry  K.  Bowman. 
(An  Inaugural  Essaj  presented  to  the  Philadelphia  College  of  Pharmacy.) 
Numerous  methods  have  been  employed  for  the  purpose  of 
determining  the  amount  of  tannin  in  astringents.  Of  these 
probably  none  are  equal  to  MuUer's,  which  appears  to  be  the 
most  definite  in  its  results  and  the  easiest  in  its  application. 
MuUer  prepares  a  standard  solution  by  dissolving  18  grammes 
of  gelatin  and  2J  grammes  of  alum  in  320  centimetres  of  water  ; 
31  cubic  centimetres  of  this  solution  precipitate  one  gramme  of 
tannin.  To  extract  the  tannin  he  powders  the  substance  con- 
taining it ;  places  the  powder  in  a  flask  and  adds  sufficient  hot 
water  to  cover  it ;  he  then  boils  it  for  a  few  moments  and  de- 
cants the  liquor  carefully  into  a  precipitating  glass.  This 
operation  is  repeated  five  or  six  times  with  more  water  and  at 
last  powder  and  all  are  poured  into  the  glass.  The  presence  of 
the  powder  does  not  interfere  with  the  precipitation  of  the 
tannin,  but  even  favors  the  clarification  of  the  liquid  ;  after 
cooling,  the  standard  solution  is  added  as  long  as  a  whitish  cloud 
is  formed  in  the  clear  liquid. 
The  principles  involved  in  Muller's  method  were  carried  out 
in  determining  the  amount  of  tannin  in  the  following  substances, 
although  the  manner  of  applying  them  was  slightly  changed. 
A  solution  of  gelatin  of  the  strength  employed  by  Muller  bein^ 
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