s?ptimberhS'}     Alcohol  in  Titration  of  Alkaloids.  479 
In  the  case  of  tropaeolin  the  diluted  alcohol  solution  required  the 
addition  of  1-5  c.c.  H2SG4  before  a  decidedly  acid  color  was 
obtained  and  satisfactory  titration  made  possible. 
After  addition  of  5  c.c.  of  alcohol  to  10  c.c.  of  the  diluted  alcohol 
solution,  the  following  results  were  obtained  : 
Per  Cent. 
With  hematoxylin  87*64 
With  tropaeoliu  00,  requiring  the  addition  of  3'3  c.c.  ^  H.2S04,  110*22 
QUININE. 
Although  quinine,  for  reasons  already  stated  above,  cannot  be 
titrated  in  the  same  manner  as  the  other  alkaloids  mentioned,  the 
effect  of  alcohol  can  nevertheless  be  observed.  Decinormal  hydro- 
chloric acid  was  used  in  place  of  sulphuric  acid  to  avoid  fluores- 
cence, and  hsematoxylin  was  employed  as  the  indicator. 
When  titrated  in  water,  the  result  showed  117-18  per  cent.;  when 
titrated  in  a  mixture  of  alcohol  and  water  (equal  volumes),  the 
result  showed  112  79  per  cent. 
It  is  possible  that  alkaloids  and  alkaloidal  residues  may  be  titrated 
with  a  fair  degree  of  accuracy  in  alcoholic  or  hydro-alcoholic  solu- 
tion, provided  the  relation  of  the  centinormal  alkali  to  the  decinor- 
mal acid  has  been  previously  determined  for  the  particular  indicator 
to  be  employed,  in  the  presence  of  the  alcohol  or  the  mixture  of 
alcohol  and  water ;  but  this  necessitates  extra  labor,  as  well  as  a 
knowledge  of  the  proportion  of  alcohol  present,  since  an  increase 
or  decrease  of  the  latter  materially  affects  the  equivalent. 
The  following  tables  show  at  a  glance  the  variation  in  the  relation 
of  alkali  to  acid,  as  indicated  by  color  reactions,  in  the  presence  of 
different  mixtures  of  alcohol  and  water.  The  presence  of  alcohol, 
moreover,  seems  to  have  a  direct  influence  on  the  color  produced 
by  the  indicator,  and  the  changes  are  by  no  means  as  sharp  as  in 
water  alone,  and  in  some  cases  are  even  observed  with  difficulty, 
thus  rendering  the  titration  results  less  reliable.  The  decinormal 
sulphuric  acid  used  was  standardized  by  precipitation  as  barium 
sulphate,  and  found  to  contain  0*004889  gramme  H2S04  in  I  c.c. 
With  this  acid  the  centinormal  alkali  solution  was  standardized, 
phenolphtalein  being  used  as  an  indicator. 
