AFebrnary^8m'}     Chemistry  of  Alkaloid  Estimations.  67 
necessary  requires  the  deft  touch,  the  accurate  eye,  and  the  patient 
mind  of  an  artist.  Especially  does  the  elaboration  of  new  and 
more  exact  methods  of  estimating  the  alkaloid  content  of  vegetable 
drugs  and  pharmaceutical  preparations  require  much  attention  to 
detail.  So  much  experimentation  of  an  apparently  empirical  char- 
acter must  be  done  that  the  scientific  nature  of  such  investigations 
is  not  always  evident.  To  emphasize  that  analytical  chemistry 
employs  the  same  fundamental  conceptions  and  facts  that  are  used 
in  other  branches  of  chemical  research  some  recent  progress  in  the 
estimation  of  alkaloids  may  be  of  interest.  The  writer  therefore 
begs  to  present,  divested  of  all  analytical  detail,  some  of  the 
advances  made  in  recent  years  in  this  important  field  of  research. 
Alkaloidal  Precipitants. — Some  fifteen  or  twenty  years  ago,  espe- 
cially in  the  United  States,  the  standard  method  of  estimating  alka- 
loids in  drugs  and  pharmaceutical  preparations  was  based  on  their 
precipitation  with  a  standard  solution  of  potassium  mercuric  iodide, 
commonly  known  as  Mayer's  solution.  The  precipitates  which 
alkaloids  formed  with  this  reagent  were  supposed  to  be  definite 
compounds  of  alkaloid  iodide  with  mercuric  iodide  containing  for 
every  molecule  of  mercuric  iodide  one,  two  or  three  molecules  of 
alkaloid  iodide.  Attempts  were  made  to  determine  for  each  alka- 
loid the  composition  of  the  precipitate  obtained  and  to  calculate 
from  the  volume  of  Mayer's  solution  used  in  each  case  the  amount 
of  alkaloid  present.  That  the  composition  of  these  alkaloidal  pre- 
cipitates was  variable  and  that  the  amount  of  alkaloid  could  not 
directly  be  calculated  from  the  volume  of  Mayer's  solution  used 
was  soon  demonstrated,  especially  by  A.  B.  Lyons  and  A.  B.  Pres- 
cott.  To-day  this  method  of  estimating  alkaloids  is  almost  forgot- 
ten. Only  occasionally  is  reference  made  to  it — as  was  recently 
done  when  Lyons,  at  a  meeting  of  the  American  Pharmaceutical 
Association,  stated  that,  in  his  opinion,  it  should  still  be  given 
preference  in  the  valuation  of  ipecac. 
Ten  to  fifteen  years  ago  the  estimation  of  alkaloids  by  means  of 
iodine  solution  (Wagner's  reagent)  was  proposed  by  Kippenberger 
in  Germany  and  by  Prescott,  Gordin  and  Gomberg  in  this  country. 
But,  again,  while  at  first  the  periodides  were  supposed  to  be  definite 
in  composition  it  was  soon  found  that  the  composition  of  these  pre- 
cipitates, consisting  of  alkaloid  iodide  plus  iodine,  and  corresponding 
to  the  composition  of  the  potassium  compound  contained  in  Lugoll's 
