TEST  FOR  THE  CINCHONA  ALKALOIDS. 
351 
The  following  varieties  of  bark  were  tested  in  this  way.  They 
were  all  about  ten  years  old,  and  had  been  well  preserved.  The 
names  given  are  those  proposed  by  Wiggers.  Peeled  and 
unpeeled  china  regia  plana,  ch.  regia  convoluta,  ch.  de  Quito 
rubra  plana  and  convoluta,  ch.  de  Bogota,  ch.  huanuco  plana  and 
convoluta,  ch.  pitayo,  ch.  de  Quito  flava,  ch.  de  cusco  vera,  ch. 
de  Carthagena  lignosa,  ch.  aurantiaca  canaliculala,  ch.  Mara- 
oaibo,  ch.  Humalies,  ch.  Loxa  vera  and  nigricans,  and  ch.  Jaen 
nigricans.  All  these  yielded  the  red  substance,  and  even  in  the 
case  of  those  barks  containing  but  small  amounts  of  alkaloids, 
the  reaction  was  distinct  and  unmistakable.  Only  in  the  case 
of  ch.  Jaen  albida  it  could  not  be  recognized.  But  the  existence 
of  alkaloids  in  this  bark  is  not  by  any  means  certain,  and  is  de- 
nied by  some. 
True  cinchona  bark  from  which  the  alkaloids  had  been  pre- 
viously extracted  by  acids,  and  false  cinchona  barks,  did  not 
yield  the  red  substance.  This  was  also  the  case  with  some  other 
kinds  of  officinal  bark  that  were  examined  for  the  sake  of  com- 
parison. Thus,  for  instance,  c.  angustura,  c.  cassice,  c.  Fran- 
gulce,  c.  copallia,  c.  geoffrogce  jamaicensis  and  surenamensis,  c. 
juglandis,  c.  pruni  padi,  c.  quercus,  c.  rharnni  cath,  c.  salicis,  c. 
ulmi,  and  c.  winter  anus. 
The  presence  of  some  substances  prevents  the  production  of 
the  red  substance,  even  in  the  case  of  true  cinchona  bark.  Among 
these  are  caustic  alkalies,  lime,  nitric  and  chromic  acids,  bichro- 
mate of  potash,  glacial  phosphoric  acid,  and  sulphuric  acid. 
In  order  to  determine  what  constituent  of  the  bark  yielded 
this  red  substance,  quinine,  cinchonine,  quinidine,  and  cinchoni- 
dine  were  severally  and  collectively  submitted  to  destructive  dis- 
tillation, but  they  did  not  in  any  case  furnish  the  red  substance. 
Quinoidine,  that  was  probably  impure,  gave  a  faint  and  only 
transient  red  coloration.  Neither  kinic  acid  nor  the  tannic  acid 
of  cinchona  gave  any  reaction.  But  any  one  or  all  the  alka- 
loids gave  the  reaction  when  heated  with  one  or  two  drops  of 
acetic  acid  for  each  grain  of  the  alkaloid.  This  was  also  the 
case  when  the  alkaloids  were  heated  with  kinic  acid  or  with  the 
tannic  acid  of  the  cinchona  bark,  and  when  heated  with  citric, 
tartaric,  valerianic,  butyric,  or  tannic  acids.  Cinchonine,  quini- 
dine, and  cinchonidine,  when  heated  with  acids,  did  not  give  the 
