390      Hypophosphorous  Acid  and  Hypophosphites.    {Am- Jour-  Pharm- 
August,  1889. 
a  few  drops  of  CaCl2,  and  rendering  slightly  alkaline  with  ammonia 
a  flocculent  precipitate  indicates  phosphate.  Carried  out  as  stated  this 
test  is  a  good  one  ;  if  phosphite  is  present  a  decided  excess  of  ammo- 
nium hydrate  will  also  cause  a  precipitate,  but  this  will  be  crystalline. 
This  test  can  be  made  quantitative  if  desirable  by  using  an  excess  of 
CaCl2  to  precipitate  all  of  the  phosphoric  acid,  as  Ca3(P04)2,  on 
addition  of  ammonia,  collecting  the  precipitate  on  a  filter,  wash- 
ing, dissolving  in  HC1,  adding  an  excess  of  ammoniacal  solution  of 
ammonium  citrate  (until  the  solution  is  alkaline  and  free  from  a  pre- 
cipitate) and  precipitating  with  magnesia  mixture.  Insoluble  hypo- 
phosphites  are  only  satisfactorily  tested  for  phosphate  by  preceding  the 
above  treatment  by  boiling  with  an  excess  of  an  alkaline  hydrate  and 
filtering. 
Sodium  and  potassium  recognized  by  flame  tests  ;  when  present  as 
impurities  were  estimated  from  the  amount  of  unsaturated  acids 
obtained  in  the  analysis. 
Calcium  detected  and  estimated  by  white  precipitate,  insoluble  in 
acetic  acid,  on  adding  ammonium  oxalate;  in  ferric  hypophosphite,. 
after  oxidation  with  Br,  by  addition  of  sufficient  ammonium  acetate 
to  precipitate  the  ferric  phosphate  on  boiling,  filtering  and  adding 
ammonium  oxalate. 
Magnesium  -  tested  for  by  addition  of  NH4C1,  NH4OH  and  (NH4)2 
C03  boiling,  filtering  and  adding  to  the  filtrate  (NH4)2HP04. 
Ferric  oxide  determined  by  taking  about  one  gram  of  ferric  hypo- 
phosphite  adding  25  cc.  water,  a  few  drops  phenolphthalein  and 
normal  NaOH  in  the  cold  until  a  red  color  is  imparted  to  the  su- 
pernatant liquid;  the  mixture  is  then  boiled  and  NaOH  added,  drop 
by  drop,  until  the  red  color  becomes  permanent.  Every  cc.  NaOH 
is  the  equivalent  of  0*0266  gm.  F203. 
From  the  results  of  these  various  determinations  was  then  calcu- 
lated the  composition  of  the  hypophosphite. 
Comparatively  little  work  had  been  done  on  the  hypophosphites 
before  the  fact  was  discovered  that  the  samples  did  not  run  evenly  in 
composition ;  the  salt  taken  for  analysis  was  afterwards  always  finely 
powdered  in  a  warm  mortar  (to  prevent  absorption  of  moisture), 
thoroughly  mixed  and  placed  in  small  tightly-stoppered  bottles  or 
test-tubes,  from  which  the  small  quantities  required  for  analysis 
were  taken,  the  weight  being  obtained  by  taking  the  difference  in 
weight  of  bottle  before  and  after  taking  the  sample. 
