Am-^1uyr;i905arm"}     Study  of  Fruit  and  Vegetable  Colors.  305 
In  observing  the  changes  recorded  in  the  above  table  it  will  at 
once  be  noticed  that  with  the  single  exception  of  strawberry,  all  of 
the  fruit  colors  change  to  either  olive  green  or  bright  green  upon 
the  addition  of  the  ammonium  hydroxide  solution  ;  and,  that  with  the 
exception  of  beet  juice  and  red  saunders,  none  of  the  other  vege- 
table reds  showed  this  distinctive  change,  the  characteristic  change 
of  the  other  vegetable  red  colors  being  mainly  to  purple  or  blue 
upon  the  addition  of  the  alkali.  It  will  also  be  seen  that  in  the 
instances  of  the  synthetic  colors,  none  showed  either  of  these  marked 
changes  upon  the  addition  of  the  alkali,  nor  have  any  other  coal-tar 
colors  which  are  in  common  use  been  observed  by  the  author  in 
which  any  marked  change  occurs  upon  the  addition  of  ammonium 
hydroxide  solution. 
The  chief  point  of  difference  between  the  synthetic  colors  and 
the  natural  vegetable  colors  is  found  in  the  fact  that  the  synthetic 
colors  may  be  deposited  upon  fat-free  woolen  goods,  by  a  test  known 
as  the  dyeing  test,  without  the  use  of  a  mordant,  while  the  vegetable 
colors  with  one  or  two  marked  exceptions  will  not  be  so  deposited 
unless  a  mordant  be  previously  used  upon  the  fabric. 
While  this  distinctive  difference  is  so  sharply  marked  as  to  make 
the  recognition  of  the  presence  of  a  synthetic  color  a  very  easy  task, 
there  are  certain  characteristic  effects  observable  even  when  the 
vegetable  colors  are  employed  in  this  test,  consequently  a  compari- 
son in  this  respect  was  considered  to  be  of  great,  importance. 
The  dyeing  test  was  performed  by  adding  5  c.c.  of  10  per  cent, 
hydrochloric  acid  solution  to  IQO  c.c.  of  the  liquid  prepared  as  in 
the  first  comparison,  then  immersing  a  piece  of  fat-free  nun's  veil- 
ing, 1x4  inches,  and  heating  at  100°  C.  for  one  hour.  The  wool 
was  then  removed  and  washed  thoroughly  in  plain  water  and  dried,. 
In  cases  where  an  appreciable  amount  of  coloring  matter  was 
deposited  upon  the  wool  by  the  first  dyeing,  a  second  dyeing  test 
was  performed  by  immersing  the  piece  of  dyed  wool  in  a  dilute 
solution  of  ammonium  hydroxide  to  dissolve  the  deposited  color, 
removing  the  piece  of  wool  after  the  color  had  been  extracted  from 
it,  acidulating  the  liquid  slightly  with  10  per  cent,  hydrochloric  acid 
solution,  inserting  a  fresh  piece  of  fat-free  wool  and  again  dyeing 
for  one  hour  at  100°  C. 
The  following  table  shows  the  results  of  this  test  when  applied  to 
the  various  colors  which  have  been  selected  for  examination  and 
comparison : 
