IODO-SULPHATES  OF  THE  CINCHONA  ALKALOIDS.  249 
at  62°  to  dissolve  1 ;  water  precipitates  it  as  a  cinnamon- 
brown  powder. 
Its  deep  marone-colored  large  aciculse  had  a  specific  gravity 
of  1.7647  at  62°. 
These  large  crystals,  exposed  whole  to  a  temperature  of  212°, 
decripitate  afterward  on  exposure  to  the  air ;  but  dried  at  212p, 
they  do  not  appear  to  lose  further  water  after  prolonged  expo- 
sure to  the  drying-bath. 
The  cinchonine  salt  exists  in  long,  acicular,  quadrilateral 
prisms,  of  a  deep  purplish-black  color,  like  that  of  elder- 
berries. 
Thin  crystals  transmit  a  yellow  tint — pure  gamboge-yellow 
when  very  thin ;  soon  passing  through  a  deep  sherry-brown  to  a 
blood-red  color,  then  a  deep  port-wine  color,  and  then  becoming 
opaque. 
These  crystals  reflect  a  deep  steel-blue  color  when  analyzed 
with  a  Nichol's  prism,  and  generally  across  the  short  diameter 
of  the  prism,  which  is  the  analogue  of  the  a-prism  of  the  quinine 
salt.  The  cinchonine  salt  possesses  doubly  absorbent  powers, 
much  more  powerfully  so  than  the  quinidin  salt,  but  inferior 
to  all  the  others,  the  body  color  is  deep  sienna  or  bistre-brown. 
These  investigations  appear  to  show  that  the  alkaloids  in  each 
instance  undergo  some  modification,  but  not  analogous  to  sub- 
stitution ;  it  appears  more  like  a  splitting-up  into  different  mole- 
cular groups,  and  a  re-arrangement  of  these  amongst  themselves, 
as  the  formulae  of  the  organic  bases  differ  much  from  those  of 
the  original  alkaloids. 
All  these  iodo-salts  possess  double  refractive  properties. 
When  the  acid  sulphates  of  the  mixed  alkaloids,  quinine, 
quinidin,  cinchonine,  and  cinchonidin,  are  dissolved  in  dilute 
spirit,  and  the  temperature  increased  to  80°  or  120°,  treat- 
ment with  tincture  of  iodine  readily  separates  the  quinine  salt 
first. 
Subsequent  further  treatment  in  the  same  manner  produces 
the  cinchonidin  salt,  more  or  less  mixed  with  the  quinine  salt. 
On  still  further  treatment,  the  quinidin  salt  is  formed  with  its 
well-marked  characters. 
The  cinchonine  salt  is  by  far  the  most  soluble  in  spirit ;  and 
