431 
ADULTERATION  OP  CHINESE  RHUBARB. 
smallest  quantities  of  Rhapontic  rhubarb  mixed  with  Chinese 
rhubarb. 
When  the  different  varieties  of  rhubarb  are  treated  with  nitric 
acid,  a  peculiar  coloration  is  produced,  which  M.  Garot  has 
designated  by  the  name  of  erythrose.  This  coloration  is  yellow 
with  the  indigenous  rhubarbs,  and  orange  with  the  exotic  kinds. 
The  essential  oils  produce  an  inverse  effect,  that  is  to  say,  Rha- 
pontic  rhubarb  produces  a  coloration  which  varies  from  orange 
to  flesh  color,  whilst  Chinese  rhubarb  experiences  no  change  of 
color. 
The  following  tables  show  the  reactions  obtained  by  means  of 
different  portions  of  Rhapontic  rhubarb  mixed  with  Chinese 
rhubarb. 
When  equal  parts  of  Chinese  rhubarb  and  magnesia  are  mixed 
together,  a  yellowish  color  is  produced ;  when  this  is  diluted 
with  a  further  quantity  of  magnesia,  and  some  essence  of  aniseed 
added,  this  coloration  remains  the  same  ;  but  when  we  take  equal 
parts  of  Rhapontic  rhubarb  and  carbonate  of  magnesia  and  add 
essence  of  aniseed,  there  is  produced  after  a  strong  trituration 
for  five  minutes  a  reddish-orange  salmon  color.  Bv  this  means 
alone  we  can  distinguish  powdered  Chinese  rhubarb  from  that  of 
Rhapontic  ;  but  my  trials  have  been  principally  carried  on  upon 
the  coloring  action  of  mixtures  of  Rhapontic  and  Chinese  rhu- 
barb. The  following  is  the  order  in  which  I  have  made  these 
trials  : — 
No.  1. 
Chinese  Rhubarb   2  grammes. 
Calcined  or  Carbonate  of  Magnesia   2  grammes. 
Essence  of  Aniseed   20  drops. 
After  trituration  for  five  minutes,  we  obtain  but  little  difference  of  coloration,. 
No.  2, 
Rhapontic  Rhubarb  .   2  grammes. 
Carbonate  of  Magnesia   2  grammes. 
Essence  of  Aniseed   20  drops. 
After  a  trituration  for  five  minutes,  we  obtain  an  organic-salmon  coloration  ; 
the  powder  attached  to  the  pestle  has  the  appearance  of  red  lead  (minium). 
No.  3. 
Rhapontic  Rhubarb   2  grammes. 
Calcined  Magnesia   2  grammes. 
Essence  of  Aniseed   20  drops. 
After  a  trituration  for  five  minutes,  we  obtain  a  very  intense  rose-salmon  col- 
oration. 
