A "dcfober Pimm ' }     ^ cidimetric  Estimation  of  A Ikaloids.  5 o  1 
be  necessary  to  prepare  some  absolutely  pure  alkaloid  ;  treat  a 
molecular  quantity  of  the  alkaloid  with  an  equivalent  of  the  acid  in 
question  to  form  a  neutral  salt,  then  add  one  drop  more  of  the 
decinormal  acid  for  an  acid  color  reaction.  For  alkaline  tints  add 
one  drop  of  the  centinormal  alkaline  solution  to  a  solution  of 
neutral  salt,  theoretically  prepared. 
In  this  work  the  writer  titrated  from  acid  to  alkaline  solutions  as 
follows  :  Brazil  wood,  from  yellow  to  onion-red,  the  purple  ulti- 
mately fading  to  this ;  cochineal,  from  yellow  to  bluish-red  ;  hema- 
toxylin, from  yellow  to  brown-orange  ;  litmus,  from  red  to  onion- 
red,  and  methyl  orange  from  red  to  straw-yellow. 
The  indicator  solutions  were  prepared  according  to  the  most 
approved  processes.  Cochineal  and  litmus  were  prepared  accord- 
ing to  the  specifications  of  Sutton's  volumetric  analysis,  sixth  edi- 
tion. Phenolphthalein,  1  gramme  dissolved  in  one  liter  of  50  per 
cent,  alcohol.  Haematoxylin,  well  crystallized,  1  gramme  dissolved 
in  100  c.c.  of  strong  alcohol.  The  method  best  suited  for  prepar- 
ing the  Brazil-wood  solution,  is  to  place  3  grammes  of  the  wood 
into  a  casserole,  add  10  c.c.  of  distilled  water,  boil  gently  for  a  few 
minutes,  cool  and  filter.  A  freshly  prepared  solution  has  given  the 
writer  the  most  satisfactory  results.  Methyl  orange,  1  gramme 
dissolved  in  1  liter  of  distilled  water.  Considerable  difficulty  was 
experienced  in  obtaining  even  a  fairly  satisfactory  product  of  methyl 
orange.  The  method  proposed  by  Mr.  B.  Reinitzer,a  for  preparing 
the  litmus  solution,  did  not  come  to  the  writer's  notice  until  con- 
siderable work  had  been  done  with  the  solution  prepared  as  above. 
In  titration,  the  following  quantities  of  the  several  indicators  were 
employed ;  methyl  orange,  Brazil  wood,  cochineal  and  phenol- 
phthalein, 5  drops  each  ;  litmus,  10  drops,  and  haematoxylin,  3 
drops. 
The  standard  solution  employed  in  this  investigation,  from  which 
the  exact  strength  of  the  other  volumetric  solution  was  determined, 
was  a  solution  of  normal  sulphuric  acid.  This  solution  was  prepared 
from  data  obtained  by  the  several  methods ;  titration  against  pure 
anhydrous  sodium  carbonate,  using  the  above  indicators ;  precipita- 
tion as  barium  sulphate,  and  Weinig'sb  process.    After  some  experi- 
a  1894,  B.  Reinitzer,  Zeit.  f.  angeicand.  Client.,  547  and  573  ;  Chent.  News, 
70.  225,  239  and  249. 
>•  1S92,  Zeit.  f.  angezuand.  Client.,  204  ;  Analyst,  17,  99. 
