118     Method  for  Estimating  Morphia  in  Opium.  {AM&r°chi%n!~ 
grains  of  potassium  chlorate,  1  fluid-drachm  of  strong  nitric  acid  and 
2  ounces  of  water.  Heat  the  mixture  until  the  iodine  is  perfectly  ox- 
idized; nearly  neutralize  with  sodium  carbonate,  then  add  an  excess 
of  solution  of  barium  chloride.  Wash  the  barium  iodate  by  decanta- 
tion,  and  boil  it  for  half  an  hour  with  a  fluid-drachm  of  strong  sul- 
phuric acid  and  3  ounces  of  water.  When  cold,  filter  and  add  water 
to  make  the  bulk  6  fluidounces. 
Sample  Solution. — If  the  opium  is  in  the  moist  state,  dry  100 
grains  on  the  water-bath,  and  after  noting  the  loss  in  weight  reduce 
it  to  fine  powder.  Put  20  grains  of  the  powder  into  a  two-ounce 
flask  with  one  grain  of  oxalic  acid  and  half  a  fluidounce  of  alcohol, 
sp.  gr.  0*838,  and,  having  attached  a  condensing-tube  to  the  flask, 
place  the  lower  part  of  the  latter  in  water  hot  enough  to  cause  the 
spirit  to  boil  gently,  and  continue  the  boiling  for  half  an  hour.  Filter 
into  a  porcelain  dish,  and  wash  the  residue  with  half  a  fluidounce  of 
hot  spirit.  Add  to  the  filtrate  half  an  ounce  of  water,  and  evaporate 
down  to  about  a  quarter  of  an  ounce,  stirring  frequently,  then  add 
an  ounce  of  cold  water.  After  the  mixture  has  stood  for  ten  minutes 
or  so,  remove  the  precipitated  resinoid  matter  by  the  filter,  and  wash 
it  with  a  little  cold  water,  adding  the  washings  to  the  filtrate.  Boil 
the  latter  with  10  grains  of  slaked  lime  for  two  or  three  minutes, 
filter,  and  wash  the  calcium  compounds  with  hot  water.  Slightly 
acidulate  the  filtrate  with  solution  of  oxalic  acid,  and  evaporate  it 
down  to  about  a  fluidounce.  After  cooling,  add  12  grains  of  caustic 
potash  and  set  aside  for  a  quarter  of  an  hour  ;  then  filter,  and  wash 
the  precipitate  with  a  drachm  of  liquor  potassae,  diluted  with  two  or 
three  times  as  much  water.  Divide  the  filtrate  into  two  exactly  equal 
portions  :  pour  one  of  these  into  a  1000-grain  measure,  add  100  grain 
measures  of  diluted  sulphuric  acid,  B,  P.,  and  water  up  to  the  mark 
and  mix  well.  Finally,  shake  the  small  quantity  of  solution  required 
for  experiment — about  half  an  ounce — with  a  fourth  of  its  bulk  of 
carbon  disulphide,  and  pass  it  through  a  filter. 
The  Experiment. — Measure  off"  with  the  pipette  100  grain  measures 
of  the  sample  solution,  and  transfer  it  to  one  of  the  trial  tubes,  add 
100  grain  measures  of  carbon  disulphide,  and,  lastly,  50  grain  mea- 
sures of  iodic  acid  solution  ;  then  immediately  close  the  tube  with  a 
sound  cork  and  shake  briskly  for  half  a  minute.  The  rose-colored 
solution  of  iodine  quickly  subsides,  but  its  brightness  is  sometimes 
rather  obscured  by  a  slight  filmy  deposit  on  the  glass.    In  this  case 
