Mar^i^sup^.}  Adulterations  of  Coffee,  Tea  and  Pepper.  157 
cloud,  which  spreads  in  streaks  through  the  water  until  the  whole  ac- 
quires a  brownish  tinge ;  with  pure  coffee,  however,  no  cloud  is  pro- 
duced until  the  lapse  of  about  a  quarter  of  an  hour.  Another  method 
of  detecting  adulteration  is  by  the  depth  of  color  obtained  by  the  in- 
fusion of  a  given  weight  of  the  suspected  article  in  water,  and  by 
the  density  of  the  infusion.  The  use  of  the  microscope,  however,  is 
indispensable.  The  ash  of  coffee,  remarkable  for  the  minute  quan- 
tity of  silica  it  contains,  and  for  the  absence  of  soda,  afforded  a  val- 
uable indication  of  its  purity. 
Adulterations  of  Tea. — Tea  is  adulterated  to  a  very  large  extent, 
not  only  with  leaves  of  various  kinds,  including  exhausted  tea  leaves, 
but  also  with  inorganic  substances,  such  as  quartz,  sand,  and  mag- 
netic oxide  of  iron ;  these  latter  substances  are  rolled  up  inside  the 
leaf,  and  one  sample  of  green  tea  examined  was  found  to  contain  no 
less  than  20  per  cent,  of  quartz  and  8*6  of  the  magnetic  oxide.  The 
latter  may  readily  be  separated  by  grinding  up  the  tea  and  removing 
the  magnetic  oxide  with  a  magnet.  The  facing  employed  for  green 
tea  usually  consists  of  French  chalk  and  Prussian  blue.  In  the  pre- 
paration of  exhausted  tea  leaves,  they  are  rolled  up  with  gum  water 
and  then  dried,  catechu  being  added  in  some  cases  to  restore  the 
^stringency.  The  article  known  as  the  "maloo  mixture"  consists 
essentially  of  exhausted  tea  leaves.  In  searching  for  the  presence  of 
leaves  other  than  those  of  the  tea  plant,  the  best  method  is  to  heat  a 
small  quantity  of  the  suspected  tea  with  water  until  the  leaves  are 
sufficiently  softened  to  admit  of  being  unfolded.  They  should  then 
be  spread  out  on  a  piece  of  glass  and  carefully  examined  as  to  the 
nature  of  the  serrations  and  the  character  of  the  venation,  also  the 
appearance  of  the  epidermis  and  the  stomata,  and  the  peculiarities  of 
the  hairs  as  shown  by  the  microscope. 
Adulterations  of  Pepper.  — The  two  kinds  of  pepper,  known  in 
commerce  as  black  and  white  pepper,  are  derived  from  the  same  plant, 
but  differ  in  the  latter  being  bleached,  or  having  the  husk  removed  by 
washing ;  but  neither  kind  can  be  adulterated  with  success  before  it 
is  ground.  The  most  common  adulterants  for  ground  pepper  are  lin- 
seed meal,  the  husks  of  mustard  seeds,  rice,  bean  and  pea  meal,  and 
the  flour  and  bran  of  the  ordinary  cereals,  ground  chilies  being  added 
to  restore  the  pungency.  Some  of  these  substances  can  be  readily 
detected  by  diffusing  the  pepper  in  water,  and  pouring  the  mixture  on 
