AXore£te*h?w.  '  Standardization  of  Digitalis  Preparations.  725 
In  this  way  any  traces  of  digitoxin  are  also  eliminated  by  "  ad- 
sorption." The  solution  is  now  evaporated  on  the  water  bath  in  the 
presence  of  chalk,  and  the  residue  purified  by  solution  in  methyl 
alcohol  and  chloroform  and  filtration.  Saponin  is  then  precipitated 
by  the  addition  of  ether,  filtered  off,  and  the  filtrate  evaporated  to 
dryness.  At  the  various  stages  aliquot  parts  of  the  solution  are 
taken  to  avoid  loss  in  nitration,  and  the  experiment  arranged  so 
that  the  final  residue  is  equivalent  to  7.5  Cc.  of  the  original  tincture. 
The  final  residue  is  dissolved  up  in  3  Cc.  of  glacial  acetic  acid.  .2 
Cc.  of  this  solution  is  then  mixed  with  2  Cc.  of  Frohde's  reagent  in  a 
4  in.  X  Vi  in.  test  tube,  allowed  to  stand  for  fifteen  minutes,  and 
the  color  produced  compared  with  the  color  chart. 
(=  Values  for  experiment  A.) 
The  color  chart  is  painted  from  actual  estimations,  and  requires 
a  little  explanation. 
The  "  Equivalent  Minimum  Lethal  Dose  "  values  are  noted  sep- 
arately under  each  color  for  each  of  the  two  colorimetric  estimations. 
The  "  relative  strength  "  values  denote  the  amount  of  glucosides 
extracted  in  the  various  colorimetric  estimations,  taking  the  color 
produced  by  the  water  soluble  glucosides  extracted  from  a  standard 
tincture  (M.L.D.  by  injection  =  0.75)  by  process  A,  as  unity. 
Process  B :  Colorimetric  for  Total  Glucosides. 
In  this  second  estimation  an  alcoholic  strength  of  70  per  cent,  is 
maintained  throughout,  in  order  to  keep  all  the  glucosides  in  solu- 
tion. The  extraneous  matter  is  removed  by  lead  acetate,  but  is  fil- 
tered off  through  ordinary  filter  paper  only,  no  kieselguhr  being 
used.  The  excess  lead  is  removed  by  sodium  phosphate,  and  the 
filtrate  evaporated  to  dryness  in  the  presence  of  chalk  to  prevent 
hydrolysis.  The  glucosides  are  dissolved  out  by  repeated  extraction 
with  chloroform,  the  solutions  being  filtered,  bulked,  and  evap- 
orated to  dryness.  Aliquot  parts  of  the  solution  are  taken  at  the 
various  stages  as  before,  to  avoid  loss  in  filtration,  and  the  exper- 
iment is  arranged  so  that  the  final  residue  is  equivalent  to  7.5  Cc. 
of  original  tincture.  The  final  residue  is  dissolved  up  in  3  Cc.  glacial 
acetic  acid.  0.2  Cc.  of  this  solution  is  taken  and  mixed  with  2  Cc. 
of  Frohde's  reagent  in  a  4  in.  X  %  in.  test  tube  as  before,  and,  after 
