532  Valuation  of  Drugs  and  Foods.       { November hi™- 
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(A)  It  has  been  the  attempt  of  the  author,  under  these  methods,  to 
work  upon  the  least  quantity  of  drug  necessary  to  obtain  appreci- 
able reactions  or  characteristic  results.  For  instance,  in  looking 
at  the  various  drugs  containing  tannin,  the  question  may  be  asked: 
"Is  it  not  as  satisfactory  to  take  100  milligrammes  (o-ioo  gramme) 
of  the  drug  and  boil  it  for  a  few  minutes  with  20  c.c.  of  water 
and  make  a  colorimetric  test  on  this  solution,  using  ammonio- 
ferric  alum  as  a  reagent,  as  it  would  be  to  make  a  solution  of  a 
larger  quantity,  and  endeavor  to  obtain  values  either  in  terms 
of  permanganate  or  by  the  hide  method,  etc.?"  Everyone  who 
has  worked  on  the  estimation  of  tannins  must  appreciate  how  un- 
satisfactory are  the  quantitative  estimations  as  usually  carried  on. 
By  boiling  the  various  drugs  containing  tannin  (as  quercus  alba, 
geranium,  kino,  catechu,  galla  and  krameria)  with  water,  in  the 
amounts  suggested  above  and  diluting,  as  necessary,  after  adding 
a  few  drops  of  a  ferric-ammonia-alum  solution,  solutions  are  ob- 
tained which  may  be  compared  in  color  to  a  standard  of  a  given 
strength. 
The  following  are  the  quantities  used  of  the  drugs  mentioned 
above,  and  the  results  obtained  therewith : 
Take  o-ioo  gramme  of  quercus  alba,  boil  with  20  c.c.  of  water; 
filter,  and  when  cool  take  5  c.c.  of  the  solution,  dilute  with  25  c.c. 
of  water;  add  ammonio-ferric  alum  solution,  and  there  is  produced 
a  faint  greenish-brown  color,  and  in  the  course  of  a  few  hours  a 
precipitate  of  the  same  color  results. 
Take  O-IOO  gramme  of  krameria,  boil  in  the  same  manner  with 
20  c.c.  of  water.  Filter,  and  when  cool  take  5  c.c.  of  the  solution, 
dilute  with  160  c.c.  of  water  ;  add  ammonio-ferric  alum  solution,  and 
there  is  produced  a  grayish-blue  color,  corresponding  in  intensity 
to  the  coloration  produced  with  quercus  alba.  It  should  be  noted 
that  a  dilution  of  over  six  times  is  necessary  to  produce  the  same 
intensity  of  color. 
Using  an  analogous  procedure  with  geranium,  it  is  found,  if 
to  5  c.c.  of  the  aqueous  solution  180  c.c.  are  added,  that,  with  a  few 
drops  of  ammonio-ferric  alum  solution,  a  coloration  of  equal  intensity 
to  that  of  solutions  of  oak  bark  or  krameria  may  be  secured. 
Five  c.c.  of  the  original  solution  of  catechu  requires  to  be  diluted 
with  200  c.c.  of  water  in  order  to  produce,  with  ammonio-ferric 
alum,  a  solution  of  like  intensity  of  color  to  solutions  of  the  preced- 
ing drugs. 
