AmAJgust.^mm'}    Hypophosphorous  Acid  and  Hypophosphites.  393 
phosphorous  acid  will  remain  unchanged  while  the  ferrous  condition 
is  oxidized  to  ferric,  there  is  another  reason  which  it  is  strange  to  say, 
has  never  been  advanced  against  the  above  process  yielding  the  officinal 
product.  In  the  change  of  ferrous  salts  into  ferric  there  must  always 
be  added  sufficient  acid  to  satisfy  the  increased  equivalence.  When  this 
acid  is  not  supplied  there  will  always  be  produced  a  basic  salt  (for 
illustrations  the  officinal  solutions  of  ferric  sulphate  answer  admirably). 
Assuming  that,  as  in  the  above  case,  the  oxidation  is  due  to  the  oxy- 
gen of  the  air  and  does  not  affect  the  hypophosphorous  acid,  the  change 
is  written  2  Fe  (H2P02)2+0==Fe2  O  (H2P02)4  a  basic  salt ;  by  the  ad- 
dition of  the  required  quantity  of  acid  there  is  produced,  theoretically, 
the  normal  salt,  2  Fe  (H2P02)2+0+2  H3P02=Fe2  (H2P02)6-f-H20. 
Further  comment  is  hardly  necessary. 
2.  By  double  decomposition  of  solution  of  ferric  chloride  or  sul- 
phate and  sodium  hypophosphite.  This  method  gives  the  desired 
officinal  product  but  is  subject  to  some  practical  difficulties.  The 
freshly  precipitated  salt  is  quite  soluble  in  water  and  by  washing,  to 
remove  the  sodium  salt,  there  is  very  little  of  the  hypophosphite  left. 
From  the  analysis  of  two  commercial  samples  (I  and  II)  the  manu- 
facturers overcome  this  difficulty  by  very  little  washing,  consequently, 
these  preparations  contain  large  quantities  of  sodium  salts,  in  both 
cases  the  sulphate. 
An  excess  of  the  iron  salt  also  increases  the  solubility,  while  (in 
making  a  preparation  described  further  on)  the  presence  of  excess  of 
hypophosphite  was  found  to  diminish  it. 
Ferric  hypophosphite  being  insoluble  in  alcohol  and  both  ferric 
chloride  and  calcium  chloride  soluble,  it  was  thought  possible  to  make 
the  salt  by  triturating  calcium  hypophosphite  and  a  slight  excess  of 
solution  of  ferric  chloride  in  the  presence  of  alcohol  and  thoroughly 
washing  the  product  with  alcohol.  The  alcohol  was  afterward  recov- 
ered by  distillation.  This  preparation  (III)  was  of  light  yellow  color 
due  probably  to  a  little  oxychloride  of  iron  which  apparently  was 
formed ;  although  containing  a  higher  percentage  of  Fe2  (H2P02)6,  the 
product  was  not  at  all  deemed  satisfactory. 
Freshly  precipitated  ferric  hypophosphite  is  flocculent  in  appearance 
but,  allowed  to  stand  sometime  before  filtering,  becomes  crytalline  and 
quite  insoluble  in  water,  therefore  permitting  a  thorough  washing  with 
little  loss.  Taking  advantage  of  this  and  allowing  for  the  purity  of 
commercial  hypophosphite  of  calcium  (98  per  cent.)  and  the  decreased 
