476  Titration  as  a  Means  of  Assaying  Drugs.  {  Am,o2tujf9*arm' 
289.  Those  of  the  two  alkaloids  of  nux  vomica,  strychnine  and 
brucine,  are  respectively  334  and  394,  and  as  we  assume  in  this  case 
that  the  two  alkaloids  are  present  in  equal  amounts,  it  follows  that 
the  molecular  weight  to  be  used  in  our  calculations  is  the  mean  of 
334  and  394,  or  364.  The  molecular  weight  of  emetine,  the  only 
alkaloid,  at  least  non-volatile  alkaloid,  of  ipecac  root,  is  generally 
admitted  to  be  496,  as  the  analyses  made  by  Glenard  1  of  the  crystal- 
lized pure  specimen  of  the  hydrochloride  of  emetine  yielded  him 
figures,  which  when  converted  into  a  formula,  gave  C^H^IN^O^H 
CI.  We  thus  see  that  C30H44N2O4(=  496)  or  one  molecule  of  eme- 
tine requires  2  HC1  to  neutralize  it,  therefore  it  requires  only  4^6.  or 
248  grammes  of  emetine  to  neutralize  1  HC1,  i.e.,  36*37  grammes  of 
HC1.  Our  next  calculation  is  to  determine  to  how  much  alkaloid 
in  grammes  is  one  cubic  centimeter  of  our  decinormal  hydrochloric 
acid  solution  equivalent  ?    We  proceed  as  follows  : 
1000  cc.  of  normal  hydrochloric  acid  contain  36*37  grammes  of  HC1. 
ice.  "  "         "       "    0-03637  wi 
1  cc.  of  decinormal       "  "        "  o-oo3637       "  " 
But 
36'37  grammes  of  HC1  will  r  364  grammes  of  nux  vomica  alkaloids, 
neutralize   and  are   hence  -  24S  grammes  of  emetine, 
equivalent  to    ...      .  .  v  289  grammes  of  mydriatic  alkaloids. 
Hence 
1,000  cc.  of  normal  HC1  are  f  364  grammes  of  uux  ™mica  alkaloids. 
equivalent  to   248  Srammes  of  emetine. 
I  289  grammes  of  mydriatic  alkaloids. 
Or 
1  cc.  of  decinormal  HC1  is  f  0^364  grammes  of  nux  vomica  alkaloids. 
equivalent  to  j  °"°248  Srammes  of  emetine. 
vo'0289  grammes  of  mydriatic  alkaloids. 
In  this  way  we  know  the  equivalent  of  1  cc.  of  decinormal  hydro- 
chloric acid  for  every  alkaloid  or  mixture  of  alkaloids,  and  can 
readily,  from  the  number  of  cubic  centimeters  of  acid  used,  calculate 
the  amount  of  alkaloid  present,  and  hence  also  the  percentage  of 
alkaloids. 
The  following  tabular  statement  of  results  will  show  the  relative 
gravimetric  inaccuracies  for  each  alkaloidal  drug  investigated  by  us 
in  case  of  each  method,  and  also  the  relative  merits  of  the  various 
methods  investigated. 
1  See  Beilstein,  "  Handbuch  der  Organischen  Chemie,"  II  edition.  Vol.  Ill, 
p.  539;  also  Husemann-Hilger,  "Die  Pflanzenstoffe, "  Vol.  II,  p.  1363. 
