444  The  Opium  Assay  Method. 
hoi  would  be  o-8  per  cent.,  but  guarding  against  loss  by  evaporation 
as  directed  and  allowing  a  loss  of  one  cubic  centimetre,  which  is 
considered  high,  the  loss  is  not  greater  than  0  05  per  cent. 
In  this  connection  two  sources  of  error  may  be  mentioned,  if  the 
washing  with  alcohol  and  ether  is  not  effected  as  promptly  as  pos- 
sible ;  the  first  addition  of  the  alcoholic  solution  to  the  water-wet 
crystals  has,  as  a  consequence,  the  formation  of  a  dilute  alcohol  in 
which  morphine  is  less  soluble  and  hence  may  crystallize  out;  the 
addition  of  ether  to  an  alcoholic  solution  of  morphine  lessens  the 
solubility  of  morphine  in  alcohol,  and  again,  a  separation  will  take 
place.  In  collecting  the  wash-liquids,  crystals  were  always  observed 
to  form,  but  never  in  the  short  time  necessary  to  carry  through  these 
operations. 
The  mother-liquors  set  aside  commenced  to  show  additional  pre- 
cipitations, the  quantity  of  these  precipitates  increased  in  the  order 
given,  6,  3,  4,  5,  2  and  1,  the  first  three  containing  notably  less  than 
the  last  three.  What  the  deposit  is  has  not  yet  been  determined  ; 
from  the  assays  1,2  and  3  it  would  seem  to  be  matter  not  morphine, 
for  we  notice  here  that  the  correction  increases  with  the  length  of 
time  for  precipitation.  The  second  precipitate  appears  to  vary 
indirectly  with  the  time  allowed  for  the  first  precipitation.  Dr. 
Squibb,  in  referring  to  the  length  of  time  necessary  for  the  precipi- 
tation of  morphine,  states  that  it  is  not  surely  complete  in  less  than 
eight  to  ten  hours,  and  considers  it  better  to  allow  it  to  stand  over 
night ;  as  the  results  obtained  in  assays  allowed  to  stand  over  night 
and  those  allowed  to  stand  only  six  hours  do  not  differ  by  more  than 
0-3  per  cent.,  the  claim  of  accuracy  made  for  the  method,  it  would 
appear  that  the  supposition  of  Dr.  Squibb  that  the  second  precipi- 
tate is  meconate  of  calcium  is,  in  the  main,  correct  (it  seems 
undoubtedly  to  be  the  mixture  of  salts  giving  rise  to  the  ash  and 
to  the  lime-water  residue). 
A  study  of  the  corrections  by  the  ignition  and  the  lime-water 
tests  shows  results  that  agree  closely  where  the  morphine,  to  start 
with,  was  practically  free  from  color ;  in  Nos.  3  and  4  the  ignition 
method  gives  a  correction  which  is  too  low,  because  the  contami- 
nating coloring  matter  is  free  from  ash,  and  hence,  the  amount  of 
color  is  recorded  as  pure  morphine  ;  this  is  another  serious  objection 
to  this  method,  although  its  use  is  extended  through  the  alcohol 
washing  successfully  removing  color,  except  when  the  precipitation 
