^'^SF*'}  Volumetric  Determination  of  Alkaloids.  639 
scarcely  be  regarded  as  an  alkaloid  and  which  is  without  action 
upon  phenolphthalein  and  litmus,  and  atropine,  which  with  these 
substances  behaves  like  a  weak  acid. 
However  it  may  be,  the  alkaloid  to  be  determined  must  be 
brought  to  the  condition  of  a  soluble  salt  by  means  of  a  mineral 
acid,  e.  g.,  sulphuric  acid,  either  in  water  or  in  a  slightly  alcoholic 
solution.  An  excess  of  acid  does  not  prevent  the  reaction,  but  on 
the  contrary  rather  promotes  it.  The  presence  of  any  salt  of  the 
alkaline  or  earthy  bases,  and  even  of  a  certain  number  of  the  heavy 
metals  (e.  g.,  zinc),  has  no  effect  upon  the  process. 
The  following  method  of  operation  is  very  easily  applicable  to  the 
determination  of  the  alkaloids  above-mentioned,  and  also  of  the 
acids  with  which  they  may  be  combined. 
Determination  of  the  Acid. — We  introduce  into  a  beaker  of 
Bohemian  glass  1  0!0  Q  part  of  an  equivalent  of  the  alkaloid  or  of  a 
salt  of  the  alkaloid,  adding  10  cc.  of  decinormal  sulphuric  acid  in 
case  of  a  salt,  or  20  cc.  in  case  of  a  free  alkaloid.  We  add  20  cc. 
of  neutral  alcohol  at  90  per  cent.,  and  three  or  four  drops  of  an 
alcoholic  solution  of  phenolphthalein.  All  the  salts  of  the  alkaloids 
dissolve  in  this  acid  alcoholic  liquid.  We  then  pour  in  decinormal 
potassa  until  there  appears  a  faint  rose-colored  tint  of  phenol- 
phthalein. The  number  of  cc.  of  decinormal  potassa  used  expresses 
all  the  acid,  free  or  combined,  existing  in  the  mixture.  The  rose- 
tint  of  phenolphthalein  appears  only  when  all  the  alkaloid  is  in  the 
free  state  in  the  liquid  ;  as  a  transparent  solution  if  the  alkaloid  is 
soluble  in  a  weak,  neutral  alcohol,  or  as  a  precipitate  if  it  is  insolu- 
ble. We  have  thus  a  mixture  indifferent  to  phenolphthalein,  but 
alkaline  to  litmus  in  consequence  of  the  liberation  of  the  alkaloid: 
Determination  of  the  Alkaloid. — Into  a  second  beaker  of  Bohe- 
mian glass  we  introduce  of  an  equivalent  of  the  alkaloid,  or 
of  a  salt  of  an  alkaloid,  with  10  or  20  cc.  of  decinormal  sulphuric 
acid,  and  then  some  drops  of  a  sensitive  tincture  of  litmus.  The 
color  is  then  rendered  blue  again  by  means  of  decinormal  potassa. 
The  number  of  cc.  of  the  alkaline  liquid  employed  in  this  second 
saturation  represents  merely  the  free  acid.  If  this  number  is  sub- 
tracted from  the  figure  which  in  the  foregoing  operation  measures 
the  entire  acid,  it  expresses  exactly  the  quantity  of  sulphuric  acid 
combined  with  the  alkaloid  in  the  state  of  a  basic  salt,  and  conse- 
quently the  weight  of  the  alkaloid  itself.    It  is,  in  fact,  sufficient  to 
