6io 
Tests  for  HypopliospJiites. 
Am.  Jour.  Pharm. 
Dec,  1890. 
greater  part  of  the  nitric  acid  be  neutralized  by  addition  of  ammonia 
the  test  succeeds  with  thiosulphate  even  in  the  cold.  With  this 
slightly  acid  ammonium  molybdate  solution,  it  is  possible  to  obtain 
a  faint  blue  color  with  sulphites  ;  this,  however,  shows  best  by  add- 
ing a  slight  excess  of  ammonia  after  warming  the  mixed  sulphite 
and  molybdate  solutions.  It  may  be  stated  here  that  this  faintly 
acid  solution  does  not  give  the  hypophosphite  test  as  readily  or  as 
nicely  as  the  more  acid  commercial  solution ;  using  this  strongly 
acid  ammonium  molybdate  solution,  the  test  for  hypophosphites  can 
be  so  modified  that  sodium  sulphite  solution,  or  even  a  small 
quantity  of  thiosulphate  solution,  may  be  used  in  place  of  sulphurous 
acid. 
In  repeating  the  tests  made  by  Millard,  it  was  found  that  stannous 
chloride,  in  moderately  dilute  solution,  invariably  gave  a  very  fine 
blue  color,  with  the  commercial  molybdate  solution  ;  the  same  test 
carried  out  with  a  concentrated  solution  of  stannous  chloride  added 
in  considerable  quantity,  gave  at  first  a  brownish  solution,  changing 
on  standing  to  a  greenish-blue.  It  was  also  found  that  ammonitfm 
molybdate  added  to  complex  solutions  containing  stannous  chloride 
produced  a  blue  color. 
From  the  above,  it  will  be  seen  that  several  reducing  agents 
besides  hypophosphites  have  the  power  of  reducing  molybdic  acid 
to  the  blue  state,  but  that  only  the  stannous  chloride  will  do  it  under 
the  same  conditions  as  the  hypophosphites.  Millard  states  in  the 
presence  of  sulphides,  thiosulphates  and  chlorates  the  test  for  hypo- 
phosphites may  be  obtained  after  these  salts  have  been  decomposed 
by  boiling  with  dilute  hydrochloric  acid.  This  is  correct  as  far  as 
the  sulphide  and  thiosulphate  are  concerned,  but  the  chlorate  boiled 
with  hydrochloric  acid  liberates  chlorine  which  oxidizes  rapidly  the 
hypophosphite  to  phosphate,  and  then  a  yellow  precipitate  is 
obtained  when  the  molybdate  solution  is  added.  In  solutions  con- 
taining stannous  chloride  this  latter  is  not  changed  by  boiling  with 
hydrochloric  acid,  and  hence  the  solution  after  boiling  will  give  the 
blue  color  with  ammonium  molybdate,  although  no  hypophosphite 
is  present. 
Considerable  interest  was  excited  after  the  above  results  were 
obtained,  as  to  the  behavior  of  sodium  tungstate  (also  given  by 
Millard  as  a  delicate  test  for  hypophosphites)  towards  the  sub- 
stances giving,  under  the  proper  conditions,  similar  tests  with  the 
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