PREPARATION  OF  CITRATE  OF  IRON  AND  QUINIA.  299 
capsule  in  a  moist  atmosphere  at  72°  for  one  hour^  lost  10  grains. 
In  nine  hours  it  had  lost  47  grains,  and  then  ceased  to  lose.  It 
was  then  placed  in  dry  air  at  a  temperature  varying  from  100° 
to  160°,  where  in  fourteen  hours  it  weighed  380  grains,  and 
ceased  to  lose.    Exposed  again  under  the  first  mentioned  condi- 
tions it,  in  sixteen  hours,  weighed  395  grains. 
Exposed  again  to  dry  hot  air  for  7  hours  it  weighed  377  grains. 
"         "      "    moist  air  at  72°  for  16  "     "       "      391|  " 
"         •<      "    hot  dry  air        "  8£  "     "       "      377  " 
«         "      "    moist  air  at  72°  "  15  «     «       «      392 1  " 
"  "      u    ordinary  air  and  temp,  fori  week,   "      392  " 
It  was  then  dissolved  and  precipitated  by  the  formula  given 
when  it  yielded  300  grains  of  quinia. 
The  contents  of  another  bottle,  weighing  432  grains  was  simi- 
larly treated.  In  five  hours  it  weighed  382  grains,  and  when 
precipitated  and  well  dried,  it  yielded  nearly  290  grains.  Other 
bottles  (three)  of  intermediate  weights  were  examined  in  a 
similar  way,  and  the  mean  yield  of  quinia  from  the  whole  was 
293i  grains  to  each  commercial  "  ounce  "  of  sulphate.  Now  as 
436  is  the  equivalent  number  of  officinal  sulphate  of  quinia,  and 
as  there  are  437.5  grains  to  the  avoirdupois  ounce,  it  follows 
that  there  should  be  about  324  grains  of  quinia,  40  grains  sul- 
phuric acid  and  72  grains  of  water  of  crystallization  in  each  com- 
mercial ounce.  But  these  experiments  give  293|  grains  of  quinia, 
36  grains  of  sulphuric  acid,  and  108  grains  df  water,  or  about  10 
per  cent,  of  uncombined  water. 
Hence,  as  a  practical  result,  it  is  safe  to  use  each  commercial 
ounce  of  this  sulphate  of  quinia  as  390  grains,  after  6  hours 
exposure  to  dry  air.  The  formula  takes  the  fifth  part  of  this, 
which  under  ordinary  management  will  yield  58  grains  of  jdry 
quinia. 
In  precipitating  quinia  the  quantity  of  solution  of  ammonia 
should  be  carefully  attended  to,  as  there  is  loss  in  using  too  little 
or  too  much.  The  washing  should  be  carefully  performed  on  a* 
strainer  of  thick  jean,  A  wash  bottle  with  small  orifice  is  well 
adapted  to  the  purpose,  the  water  being  allowed  to  trickle  from 
it,  and  being  continuously  distributed  over  the  whole  surface  fof 
the  precipitate.  In  this  way,  the  washing  can  be  perfectly  done 
in  15  minutes  with  f,  3 10  of  water,  and  the  loss  then  is  small, 
