OPTICAL  CHARACTERS  OF  CERTAIN  ALKALOIDS.  247 
The  excess  arises  from  the  hydrogen  twice  calculated  in  water  of 
crystallization. 
These  numbers  agree  very  closely  with  the  formula 
(C35  H19  N2  OM- P)  SO3  HO+5HO, 
and  prove  it  to  be  the  sulphate  of  iodo-quinidine,  very  analogous 
to  the  optical  quinine  compound,  yet  differing  materially  in  its 
optical  properties. 
There  is  another  alkaloid  frequently  associated  with  quinidine, 
which  also  crystallizes  from  spirit  in  the  prismatic  form  like 
quinidine  and  cinchonidine,  but  is  another  example  of  epipolism 
or  fluorescence.  Its  iodo-sulphate  is  deep  olive-green  in  its  re- 
flected tint,  orange-yellow  by  transmitted  light,  and  possessing 
in  an  eminent  degree  optically  doubly  absorbent  powers,  thin 
laminae  being  quite  black,  but  still  thinner  ones  give  a  bistre- 
brown  «  body-color"  when  polarized  perpendicular  to  axis. 
This  alkaloid  was  also  furnished  me  by  the  kindness  of  Mr. 
Howard,  but  has  not  yet  been  sufficiently  purified,  or  in  the 
quantity  necessary  to  give  certain  results. 
It  possesses  one  very  peculiar  property.  When  dissolved  in 
chloroform  and  evaporated  spontaneously  on  glass,  the  gummy 
and  uncrystalline  residue,  mounted  in  Canada  balsam,  at  once 
shows  a  deep  blue-green,  epipolic  or  fluorescent  appearance. 
Pure  cinchonidine  does  not  possess  epipolic  dispersion  and 
does  not  become  green  by  chlorine-water  and  ammonia  ;  and 
when  it  is  dissolved  in  acetic  acid  or  chloroform  and  the  fluid  is 
exposed  on  glass  plates  to  spontaneous  evaporation,  beautiful 
crystals  in  circular  spots  or  drusse  develope  themselves,  which 
under  polarized  light  exhibit  black  crosses  and  white  or  colored 
sectors. 
These  appearances  are  not  exhibited  by  pure  quinine  or  true 
quinidine  (^-quinine),  both  of  which  give  a  gummy,  uncrystalline, 
and  perfectly  transparent  residue. 
Pure  cinchonidine,  thus  optically  and  chemically  distinguish- 
able from  either  quinine  or  quinidine,  is  still  further  remarkable 
for  producing  with  sulphuric  acid  and  iodine  an  optical  doubly 
absorbent  compound  of  intense  power,  even  equal  to  the  sulphate 
of  iodo-quinine  compound ;  these  crystals  are  very  similar  in 
form  to  my  artificial  tourmalines,  and  have  long  been  mistaken 
by  me  for  them  ;  even  at  present  I  can  only  distinguish  them  by 
