60  Frcehdes  Reagent  a  Test  for  Morphia.  {Am-FJe°bur;876harm' 
grains  ammonium  molybdate  in  2  drachms  sulphuric  acid  (i  part  to  15), 
extended  the  results,  positive  and  negative,  by  this  test  to  over  twenty 
alkaloids  and  glucosides.  And,  about  the  same  time,  DragendorfF, 
using  fresh  solutions  of  1  milligram  sodium  molybdate  in  one  cub. 
cent,  of  concentrated  sulphuric  acid  (1  part  in  1840  parts),*  obtained 
and  reported  results,  positive  and  negative,  with  50  alkaloids  and  glu- 
cosides.f 
For  morphia,  Dragendorff  names  Frcehde's  test  first.  J  In  his  very 
valuable  "  Untersuchungen,"  ii,  233,  Hager  gives  a  table  of  the  re- 
actions which  Dragendorff  determined,  using  the  1  to  1840  molybdic 
solution.  I  know  of  no  better  authority  in  proximate  analysis  than 
the  indefatigable  Dorpat  professor  Dragendorff.  His  thorough  research 
in  the  separation  of  alkaloids  gives  good  assurance  of  the  purity  of  those 
with  which  he  experiments.  For  my  own  satisfaction,  I  have  tried 
the  larger  number  of  the  tests  he  reports  with  Froehde's  reagent,  and  I 
have  found  his  results  verified  with  all  that  I  have  tried. 
It  it  very  true  that  the  reduction  of  molybdic  acid  produces  blue  pro- 
ducts of  various  shades  (hydrated  molybdic  molybdates),  and  also  by 
further  reduction  a  brown  product  (molybdic  hydrate)  and  that  numer- 
ous reducing  agents — inorganic  and  especially  organic — effect  these 
reductions.  Indeed,  a  solution  of  molybdic  acid  in  sulphuric  acid  is 
deoxidized  to  a  blue  precipitate  by  heat  alone,  at  the  temperature  of 
incipient  vaporization  of  the  sulphuric,  that  being  an  approved  test  for 
molybdenum. § 
Now  a  large  proportion  of  the  most  certain  tests  for  organic  com- 
pounds are  made  by  application  of  oxidizing  agents  which  serve  to 
reveal  the  reducing  power  of  these  compounds  :  the  degree  and 
kind  of  the  reducing  power  being  within  certain  limits  characteristic  of 
each  reducing  agent  tested  for.  Trommer's  test  for  sugars,  the  "  fad- 
ing purple"  test  for  strychnia,  and  the  "  thalleioquin  test"  for  quinia, 
are  examples  :  the  old  tests  for  morphia  by  nitric  and  iodic  acids, 
and  probably  that  by  ferric  chloride,  are  of  the  same  kind.  In  the 
greater  number  of  these  tests,  chemists  have  not  ascertained  what  are 
*  For  "  o*oi  grain,"  at  middle  of  page  22  this  vol.  of  this  Journal,  read  "  o-oi 
gram." 
f  "  Beitrage  zur  gericht.  Chemie  einzelner  organischer  Gifte,"  St.  Petersburg, 
1872. 
X  "  Die  chem.  Werthbestimmung  starkwirlcender  Droguen,"  p.  81. 
§  Schonn  :  "  Zeitsch.  f.  analyt.  Chemie,"  viii,  (1869),  379. 
