AnseJp°tur'i92iarm' }        Titration  of  Certain  Alkaloids. 
659 
It  may  be  noted  that  the  statement  frequently  seen  in  the  text- 
books that  a  solution  of  morphine  hydrochloride  is  neutral  to  litmus 
is  unfounded.  Pure  morphine  hydrochloride  should  be  acid  to  lit- 
mus. Two  commercial  samples  of  morphine  hydrochloride  in  1  per 
cent,  solution  had  a  Ph  =  4.83  and  4.50  respectively,  showing  a 
slight  excess  of  morphine  over  hydrochloric  acid  present.  A  sam- 
ple of  morphine  crystals  when  titrated  to  the  above  end-point  gave 
101.4  per  cent,  morphine  (hydrated),  showing  them  to  be  slightly 
effloresced. 
THE  TITRATION  OF  QUININE. 
Allen's  "Commercial  Organic  Analysis/'  Vol.  V,  page  514, 
states  that  "Quinine  is  a  strong  base,  completely  neutralizing  acids 
and  forming  crystallizable  salts  having  a  slight  alkaline  indication 
to  litmus.  Quinine  also  forms  a  series  of  acid  salts  which  are  neu- 
tral to  methyl  orange." 
Squire's  "Companion"  states  that  "Quinine  hydrochloride  is 
neutral,  or  at  the  most  but  faintly  alkaline,  in  reaction  towards  litmus 
paper.  It  is  usually  recommended  in  the  textbooks  to  titrate  quinine 
salts  to  phenolphthalein.  In  this  way  the  whole  of  the  quinine  is 
precipitated  in  the  course  of  the  titration,  and  the  end-point  is  not 
very  satisfactory. 
A  sample  of  carefully  -purified  quinine  free  from  other  cin- 
chona alkaloids  was  dehydrated  by  heating  to  1200. 
0.6744  gm.  anhydrous  quinine  was  dissolved  in  41.60  cc.  N/10 
hydrochloric  acid,  thus  forming  quinine  acid  hydrochloride,  and 
diluted  to  1  per  cent.  The  Ph  of  this  solution  was  then  determined 
and  found  as  a  mean  of  three  experiments  to  be  3.40. 
Quinine  acid  hydrochloride  should  therefore  in  1  per  cent,  solu- 
tion be  neutral  to  brom-phenol  blue,  with  which  it  should  give  a 
pale  greenish-yellow  color.  Methyl  orange  would  be  decidedly 
pink  at  this  Ph. 
0.7144  gm.  anhydrous  quinine  was  dissolved  in  22.03  cc.  NN/io 
hydrochloric  acid  and  diluted  to  1  per  cent.,  forming  the  neutral 
hydrochloride.    The  Ph  of  this  solution  was  as  a  mean  5.15. 
A  solution  of  this  Ph  is  neutral  to  methyl  red,  with  which  it 
gives  an  orange  color.  It  will  be  seen  from  the  above  results  that 
we  can  most  accurately  titrate  a  solution  of  quinine  hydrochloride  or 
sulphate  by  adding  standard  acid  until  a  pale  greenish-yellow  color 
corresponding  to  Ph  =  3.4  is  obtained.  A  commercial  sample  of 
