Am.  Jour.  Pliarm.  i 
March,  1890.  J 
Colorimetric  Method  for  Tannin. 
119 
high  standing.  Both  samples  melted  at  1880  C.  I  had  taken  the 
precaution  of  subjecting  each  one  to  Vitali's  test.  They  were  laevo- 
gyre.  (Atropine  is  optically  inactive.)  Their  gold  double  salt  had  a 
melting  point  of  1500  C.,and  was  in  brilliant,  golden  colored  scales, 
procured  in  the  usual  analytical  way.  They  did  not  have  the  form 
of  the  salt  reproduced  by  Wormley  (Microchemistry  of  Poisons, 
Plate  xiii,  Fig  2);  but  I  may  state  that  broken  glass  has  macro- 
scopically  about  the  same  appearance  as  the  gold  double  salts  of  the 
two  samples  of  atropine  sulphate  had  under  a  magnifying  power  of 
100  diameters. 
This  experience  is  in  accord  with  the  observations  of  others,  and 
leads  to  the  conclusion  that  the  atropine  sulphate  used  in  our  drug 
stores  at  the  present  time  is  in  reality  hyoscyamine  sulphate. 
COLORIMETRIC  METHOD  FOR  ESTIMATING  TANNIN  IN 
BARKS,  ETC. 
By  Samuel  J.  Hinsdale,  Fayetteville,  N.  C. 
Read  at  the  Pharmaceutical  Meeting,  February  18. 
Dissolve  004  gram  potassic  ferricyanide  in  500  cc.  water,  and 
add  to  it  1*5  cc.  (about  22  drops)  liquor  ferri  chloridi.    Call  this 
Iron  Mixture. 
Dissolve  o  04  gram  "  pure  "  tannin  (gallotannic  acid),  which  has 
been  dried  at  21 2°  F.,  in  500  cc.  of  water.  Call  this  Tannin 
Solution. 
Exhaust  o-8  gram  oak  bark  with  boiling  water,  and  make  it  up 
to  500  cc.  with  cold  water. 
Place  six  2  ounce  clear  glass  tumblers  (or  Beaker  glasses)  on  a 
white  surface,  and  in  one  of  them,  with  a  dropping  pipette  (about 
four  inches  long  and  one-quarter  inch  wide)  about  half  filled,  put 
five  drops  of  the  infusion  of  bark,  and  in  the  others,  with  the  same 
pipette  (after  rinsing),  put  4,  5,  6,  7  and  8  drops  of  the  "  tannin  solu- 
tion." (The  drops  of  the  infusion  and  of  the  tannin  solution  must  be 
uniform.  The  use  of  the  same  pipette,  about  half  filled,  insures 
that.) 
Now,  add  to  each  5  cc.  of  "  iron  mixture,"  and  in  about  one  min- 
ute add  to  each  tumbler  about  20  cc.  water,  and  within  three  min- 
utes observe  the  shades  of  color.  The  number  of  drops  of  "  tannin 
solution  "  used  in  the  tumbler  which  corresponds  in  shade  of  color 
