^SEyjSS.1"'}       Substitute  for  Ethyl  Alcohol.  13 
the  upper,  dark  stratum  should  be  observed  and  measured.  The 
chloroform-ether  solution  is  then  drawn  off  into  a  tared  flask  of 
about  100  c.c.  capacity,  and  the  flask  is  immersed  in  a  hot  water- 
bath  so  that  the  chloroform-ether  may  be  boiled  off  by  the  time 
another  washing  is  ready.  In  the  meantime  40  c.c.  more  of  chloro- 
form-ether has  been  added  to  the  contents  of  the  separator,  and  the 
shaking,  separating  and  drawing  off  into  the  flask  repeated.  This 
second  washing  may  or  may  not  be  then  followed  by  a  third,  man- 
aged in  the  same  way,  if  required. 
If  after  standing,  to  separate  completely  a  second  time,  the  dark 
liquid  on  top  shall  be  found  to  have  increased  in  depth,  the  indica- 
tion is  that  emulsion  has  been  formed  to  that  extent,  and  that  the 
chloroform  forming  that  emulsion  holds  the  proportion  of  alkaloids 
present  in  solution  at  the  time  that  emulsion  was  formed,  and  as  the 
chloroform  cannot  be  washed  out  of  an  emulsion,  so  the  alkaloids 
held  by  that  chloroform  cannot  be  washed  out.  Therefore,  in  the 
case  of  any  considerable  amount  of  emulsion  after  the  chloroform- 
ether  solution  is  drawn  off  into  the  flask,  the  dark  liquid  is  drawn 
off  into  the  flat  capsule  and  warmed  on  a  water-bath  until  all  the 
chloroform-ether  is  driven  off.  The  dark  liquid  is  then  returned  to 
the  separator  and  again  washed  as  before.  If  a  small  amount  of 
emulsion  again  forms,  as  very  rarely  occurs,  the  chloroform  in  it 
holds  so  very  little  alkaloid  as  to  be  within  the  limit  of  error  of  the 
method. 
The  tared  flask  wiil  then  contain  the  total  chloroform  extract, 
and  the  weight  of  this  was  long  erroneously  accepted  as  the  weight 
of  alkaloids. 
Then  10  c.c.  of  decinormal  sulphuric  acid  is  carefully  measured 
from  a  burette  into  the  flask,  and  is  rinsed  round  and  warmed  by 
immersion  in  a  water-bath  until  the  soluble  alkaloids  are  dissolved, 
when  the  insoluble  residue  will  show  that  much  of  this  extract  is 
not  alkaloid. 
Then  20  c.c.  of  hot  water  is  added  to  the  contents  of  the  flask, 
and  a  definite  quantity  (10  drops)  of  logwood  indicator.  The  color 
is  then  closely  observed  by  transmitted  light,  and  matched  by  a 
similar  quantity  of  liquid  in  a  similar  flask.  Decinormal  potassium 
hydrate  is  now  dropped  in  from  a  burette  until  the  color  changes 
slightly  to  a  pinkish  tint  or  shade  of  the  original  yellow  by  trans- 
mitted light,  and  when  this  hardly  perceptible  change  is  now  looked 
at  by  reflected  light  the  pink  tint  is  very  distinct. 
