464 
Alkaloidal  Assays. 
/  Am.  Jour.  Pharm. 
1     October,  1899. 
II. 
•AS  A  HOT  EXTRACTION  METHOD. 
Instead  of  the  cold  percolation,  as  above  directed,  hot  extraction 
in  any  suitable  apparatus  may  be  used,  all  other  features  of  the 
operation  being  the  same.  If  a  Soxhlet  tube  is  used,  care  should 
be  taken  that  the  syphon  works  intermittently,  as  otherwise  the  ex- 
traction is  very  incomplete  ;  if  Dunstan  and  Short's  apparatus1  is 
used,  the  boiling  of  the  solvent  should  be  so  regulated  as  to  have 
always  a  layer  of  about  2  centimeters  of  it  on  the  top  of  the  drug. 
Our  experience  has  taught  us  that  for  quantitative  work  cold 
extraction  by  percolation  requires  less  skill  and  care  than  hot 
extraction  in  a  Soxhlet  tube,  though  with  careful  operation  the  latter 
method  is  preferable. 
THE  VOLUMETRIC  ESTIMATION  OF  ALKALOIDS  BY  PRECIPITATION  WITH 
Estimation  by  Formation  of  a  Periodide,  so  far  Applied  to  Atropine, 
Morphine,  Stryc/mine,  Brucine,  Emetine,  Hydrastine  and  Caffei?ie. 
For  opium  assay,  see  p.  466. 
For  assay  of  nux  vomica,  with  separation  of  strychnine  from 
brucine,  see  p.  470. 
For  assay  of  ipecac,  see  p.  472. 
For  estimation  of  berberine  in  assay  of  hydrastine,  see  p.  472. 
For  estimation  of  caffeine,  the  alkaloidal  solution  must  be  invari- 
ably acidulated  (Gomberg,  1896).  For  assay  of  kola,  see  Knox  and 
Prescott,  1896-97,  "Proc.  Am.  Phar.  Assoc.,"  p.  128,  and  4.5,  p 
131  ;  Jour.  Am.  Chem.  Soc.,  ig,  p.  63  ;  20,  p.  34. 
The  Reagents  and  Utensils  Required  in  the  Volumetric  Work. 
(1)  A  standardized  solution  of  iodine  dissolved  in  water  with 
iodide  of  potassium  to  be  of  about  decinormal  strength  (12-653 
grammes  of  free  iodine  in  1,000  ex.).  The  solution  may  be  made 
as  the  volumetric  test  solution  of  iodine  of  the  U.S.P.,  and  used 
with  the  exact  decinormal  factor  of  iodine  if  preferred. 
(2)  A  solution  of  sodium  thiosulphate,  of  about  decinormal 
strength,  standardized  to  known  ratio  with  the  iodine  solution.  The 
1  Pharm.  Jour.  (3),  xiii,  664. 
2  These  directions  were  given  in  substance  in  an  article  entitled  "  Emetine 
Octoiodide  and  the  Estimation  of  Alkaloids  Generally,"  by  the  authors  of  this 
paper,  in  Jour.  Am.  Chem.  Soc,  2/,  p.  234,  March,  1899  !  Pharm.  Review,  Vol. 
17,  1899. 
FREE  IODINE.2 
