ON  THE  MEDICINAL  HYPOPHOSPHITES. 
119 
phoric  acid.  When  the  strong  odor  of  phosphuretted  hydrogen 
ceases  to  be  given  off,  the  liquid  contains,  besides  the  excess  of 
lime,  nearly  half  of  the  phosphorus  as  phosphate  of  lime,  and  the 
remainder,  deducting  the  considerable  portion  which  has  escaped 
into  the  air  as  phosphuretted  hydrogen,  as  hypophosphite  of  lime. 
According  to  Wurtz,  more  than  one  equivalent  of  water  is  de- 
composed, and  the  phosphuretted  hydrogen  is  accompanied  by 
free  hydrogen.  If  this  be  true,  the  source  of  the  super  oxidation 
of  so  much  of  the  phosphorus  is  tracable  to  the  resulting  oxygen  ; 
but  Rose  is  of  the  opinion  that  this  oxygen  is  derived  from  the 
atmospheric  air  in  contact  with  the  boiling  liquid.  When  the 
process  is  conducted  in  a  flask,  it  requires  a  constant  ebullition 
of  the  liquid  to  prevent  the  explosion  consequent  upon  the  en- 
trance of  the  atmospheric  air.  To  avoid  this  result,  it  has  been 
found  safer  to  employ  a  deep,  open  vessel.  The  constant  evolution 
of  gas  and  vapor,  which  keeps  a  froth  on  the  surface,  excludes  the 
atmosphere  in  a  great  degree,  so  that  the  yield  is  not  much  di- 
minished, whilst  the  safety  and  easiness  of  the  process  is  greatly 
increased.  The  process  should  be  conducted  under  a  hood  with  a 
strong  draught,  or  in  the  open  air,  to  avoid  the  disagreeable 
fumes  which  are  evolved. 
Take  of  Lime,  recently  burned  ...  4  lbs.  av. 
Phosphorus  .  .  .  .  1  lb.  <• 
Water  .  .  ...  5  gals. 
Slake  the  lime  with  a  gallon  of  the  water,  put  the  remainder 
in  a  deep  boiler,  and  as  soon  as  it  boils  add  the  slaked  lime,  and 
mix  to  a  uniform  milk.  The  phosphorus  is  now  added,  and  the 
boiling  is  kept  up  constantly,  adding  hot  water  from  time  to  time, 
so  as  to  preserve  the  measure  as  nearly  as  may  be,  until  it  is  all 
oxidized  and  combined,  and  the  strong  odor  of  the  gas  has  dis- 
appeared. The  mixture  froths  much,  and  but  little  of  the  phos- 
phorus reaches  the  surface.  Then  filter  the  solution  through 
close  muslin,  wash  out  that  portion  retained  by  the  calcareous 
residue  with  water,  and  evaporate  the  filtrate  till  reduced  to  six 
pints.  The  concentrated  liquid  should  now  be  re-filtered  to  re- 
move a  portion  of  carbonate  of  lime  which  has  resulted  from 
the  action  of  the  air  on  the  lime  in  solution,  and  again  evapo- 
rated till  a  pellicle  forms,  when  it  may  be  crystallized  by  stand- 
ing in  the  drying  room,  or  the  heat  may  be  continued  with 
