-586  A  Study  of  the  Use  of  Mayer's  Reagent.  {Am-T>™T^&TB1 
Gelsernine  gives  results  which  vary  considerably,  especially  with 
the  degree  of  acidity  of  the  solution.  The  titration  method  is,  how- 
ever, a  useful  one  in  the  case  of  this  alkaloid,  because  it  is  somewhat 
difficult  to  separate  it  in  a  pure  condition,  and  the  quantity  contained 
in  the  drug  is  at  most  small.  If  the  solution  contains  1  :  200  of  alka- 
loid, the  titration  equivalent  may  be  taken  as  9*5  mg. 
Hydrastine. — Results  vary  greatly,  according  to  the  degree  of  dilu- 
tion of  the  solution.  It  will  rarely  be  advisable  to  attempt  estimation 
of  the  alkaloid  by  titration.  The  following  rule  may,  however,  be 
formulated  :  Correct  the  result  by  subtracting  for  each  cc.  of  fluid 
present  at  the  end  of  the  titration  0*025  cc,  and  multiply  the  remain- 
der by  14*9,  to  obtain  the  quantity  of  hydrastine  in  milligrams. 
Hyoseyamine  resembles  atropine  in  its  behavior.  The  number  of 
experiments  made  with  it  was  not  sufficient  to  serve  as  a  basis  for  any 
useful  deductiows.  It  must  be  understood,  of  course,  that  this  alka- 
loid is  accompanied  in  the  drugs  in  which  it  occurs  by  others,  and 
that  therefore  there  is  rarely  occasion  to  make  an  estimation  of  it  by 
Mayer's  reagent. 
3forphine. — In  solutions  containing  1:200  to  1:400  Mayer's  reagent 
produces  a  white  precipitate  which  momentarily  takes  a  yellowish 
shade,  and  then  the  whole  fluid  sets  into  a  translucent  jelly  from  crys- 
tallization of  the  precipitate;  only  tolerably  strong  solutions  are  pre- 
cipitated by  the  reagent  immediately,  the  limits  of  the  reaction  for 
practical  purposes  being  reached  in  solutions  containing  1:2000, 
although  weaker  solutions,  up  to  1:3600,  may  show  a  distinct  precipi- 
tate. This  is  in  strong  contrast  with  the  behavior  of  most  of  the 
alkaloids,  which  are  precipitated  copiously  in  solutions  containing 
1:30,000  to  1:80,000. 
In  the  more  dilute  solutions  of  morphine,  the  precipitate  assumes 
the  form  of  distinct  crystals.  In  titrating  a  morphine  solution  with 
Mayer's  reagent,  a  point  is  soon  reached  where  the  solution  gives  no 
precipitate,  either  with  Mayer's  reagent  or  with  a  fresh  morphine  solu- 
tion. Just  before  reaching  this  point,  the  solution  is  observed  to  give 
with  the  reagent,  after  a  few  seconds,  a  translucent  gelatinous  precipi- 
tate, resembling  exactly  precipitated  alumina.  The  filtrate  from  this 
precipitate  in  a  few  hours  yields  distinct  crystals.  Estimation  of 
morphine  by  Mayer's  reagent  is  not  to  be  recommended,  and,  of 
course,  is  wholly  inapplicable  to  preparations  of  opium. 
Pilocarpine. — Comment  on  the  results  of  experiments  tabulated 
