Am.  Jour.  Pharm.  1 
April,  1901.  J 
Indicators  in  Nature. 
175 
Mr.  G.  H.  Whiting,  a  student,  about  this,  he  mentioned  that  the 
juice  of  the  blackberry  had  the  properties  of  an  indicator.  These 
observations  led  to  the  work  about  to  be  described.  Since  com- 
pleting it,  the  writer  has  been  informed  that  a  lady  placed  some 
violets  in  ammonia  water  to  preserve  them,  and  to  her  astonish- 
ment they  became  green. 
The  results  of  this  work  show  that  indicators  are  of  very  common 
occurrence  in  nature.  .Some  seventy-four  kinds  of  colored  flowers, 
both  wild  and  cultivated,  the  leaves  of  five  varieties  of  coleus,  the 
cow-pea  bean,  the  blackberry,  mulberry,  smilaxberry,  strawberry 
and  the  red  beet  were  extracted  with  water  or  dilute  alcohol,  and 
the  extract  tested  for  indicators.  In  only  three  cases  did  the  extract 
not  become  one  color  when  acid  and  another  color  when  alkaline. 
'As  a  rule,  the  coloring  matter  was  fairly  sensitive  as  an  indicator, 
being  changed  by  from  less  than  one  to  two  drops  of  tenth-normal 
ammonia.  Some  of  the  changes  were  very  sharp,  and  many  of  the 
colors  were  very  beautiful.  In  some  cases  the  color  passed  through 
several  stages  in  going  from  acid  to  alkaline,  or  the  reverse. 
The  materials  examined  could  be  grouped  in  four  classes : 
Class  I. — Extract  not  affected  by  acid  or  alkali. 
Class  II. — Extract  colorless  when  acid,  yellow  when  alkaline. 
The  flowers  in  this  class  were  yellow,  and  the  yellow  coloring 
matter  was  hardly  affected  by  the  extracting  agent. 
Class  ///.—Extract  red  (or  a  shade  of  red)  when  acid,  yellow 
when  alkaline. 
Class  IV. — Extract  red  when  acid,  green  when  alkaline. 
Classes  III  and  IV  are  not  sharply  separated,  sometimes  the 
color  produced  by  the  alkali  being  such  that  it  was  hard  to  decide 
whether  it  was  yellow-green  or  green-yellow.  Ammonia  was  the 
alkali  used;  often  a  green  solution  with  ammonia  would  have  been 
yellow  with  caustic  soda.  Most  of  the  coloring  matters  in  these 
two  classes  were  very  sensitive.  In  many  cases  the  flowers  were 
bleached  when  boiled  with  water,  and  the  extract  nearly  colorless, 
or  quite  so ;  but  it  would  become  colored  when  made  acid  or  alka- 
line. 
Class  V. — Miscellaneous.  This  includes  all  that  do  not  fall  in 
the  other  four  classes.  It  must  be  observed  that  in  no  case  do  the 
colors  occur  in  the  reverse  order  from  those  in  the  other  classes — 
that  is,  never  colorless  when  alkaline  and  yellow  acid,  or  red  when 
alkaline  and  green  or  yellow  acid. 
