246 
OPTICAL  CHARACTERS  OF  CERTAIN  ALKALOIDS. 
and  recent  experiments  have  shown  me  that  a  small  per-centage 
of  quinidine  was  the  cause  of  the  epipolic  dispersion  found  by  you 
in  the  specimen  of  cinchonidine  sent  by  me. 
It  may  be  as  well  to  state  that  the  cinchonidine  tested  by 
water  of  chlorine  and  ammonia  gave  no  evidence  of  green  tint, 
which  it  would  have  done  if  only  _l_dth  part  of  either  a-quinine 
or  quinidine  had  been  present,  according  to  some  recent  experi- 
ments of  my  own. 
I  have  also  found  that  1  gr.  of  pure  quinine  or  quinidine  in 
35,000  of  water  will  give  an  evident  "  epipolic"  appearance ; 
whilst  when  diluted  with  70,000  grs.  of  water  we  have  still  very 
evident  appearance  of  "  flourescence"  upon  the  perpendicular 
wall  of  the  glass  vessel  exposed  to  the  incident  light ;  whilst  a 
bluish  milkiness  of  "  internal  dispersion"  may  be  seen  when  1 
gr.  of  either  alkaloid  is  diluted  with  700,000  grs.  or  10  gallons 
of  distilled  water,  well  acidulated  in  all  these  cases  with  sulphuric 
acid. 
Some  other  interesting  results  have  followed  from  these  in- 
vestigations. When  quinidine  is  dissolved  in  an  excess  of  diluted 
sulphuric  acid,  and  the  solution  mixed  with  about  twice  its  bulk 
of  spirit,  and  warmed  to  130°  F,,  and  tincture  of  iodine  then 
added  in  sufficient  quantity,  and  subsequently  set  in  repose, 
beautiful  red  acicular  crystals  are  deposited ;  these,  upon  re- 
crystallization  from  rectified  spirit,  acquire  an  increased  size, 
become  beautiful  quadrilateral  prisms,  leaving  a  deep  garnet-red 
by  transmitted  light,  and  possessing  a  clear  bluish-purple  re- 
flected tint ;  they  are  optically  doubly  absorbent  in  a  slight 
degree,  and  transmit  a  brownish-orange  body-color  when  polar- 
ized perpendicular  to  axis.  The  primary  form  appears  to  be  a 
rhombic  prism,  and  as  far  as  my  present  analyses  go,  appears  to 
possess  centesimally  the  following  compos 
Iodine 
Sulphuric  acid 
Carbon 
Hydrogen 
Nitrogen 
Oxygen 
Water 
tion  : — 
39-665 
6-273 
32-890 
3-960 
4400 
5-040 
8-504 
100-712 
