Am.  Jour.  Pharni.  \ 
June,  1885.  J 
Certain  Aerated  Beverages. 
299 
recalling  nitrous  acid.  This  suspicion  as  to  the  presence  of  nitro- 
compounds was  confirmed  on  the  application  of  the  well-known  iron 
test.  A  given  volume  of  the  acid  was  next  treated  with  an  excess  of 
pure  sulphuric  acid  and  metallic  mercurVj  and  the  voluuie  of  nitric 
oxide  evolved  was  measured.  It  gave  gas  corresponding  to  the  follow- 
ing amounts  of  nitrogen  :  One  hundred  pints  of  the  acid  yielded  four 
and  a  half  pints  of  nitrogen,  equivalent  weight  for  weight  to  '003  per 
cent,  of  nitrogen.  Beyond  traces  of  iron  no  other  impurity  was  de- 
tected. 
At  this  stage  the  following  experiments  were  instituted.  Into  a 
soda-water  bottle  were  put  suitable  quantities  of  the  ginger  essence, 
syrup  and  calcium  carbonate,  and  water  to  nearly  fill  it.  Then  suffi- 
cient of  the  contaminated  acid  was  added  to  decompose  the  lime,  and 
the  contents  of  the  bottle  were  immediately  secured  by  a  cork  wired 
down.  Repetition  experiments  were  made,  in  which  a  portion  of  the 
ginger  essence  was  replaced  by  capsicine  and  gingerine,  and  others  in 
which  a  pure  acid  was  substituted  for  the  impure  oil  of  vitriol.  The 
bottles  were  opened  at  varying  intervals,  when  the  following  observa- 
tions were  made.  Those  in  which  the  impure  acid  had  been  used  showed 
a  marked  decrease  in  pungency  at  the  end  of  two  hours ;  at  the  end  of 
four  hours  the  pungency  was  faint;  at  the  end  of  six  hours  it  had 
completely  disappeared.  The  ginger  essence,  gingerine  and  capsicine 
had  been  affected  apparently  to  the  same  degree.  Those  in  which  the 
pure  acid  had  been  used  had  retained  their  pungency  apparently  in  its 
entirety. 
These  results,  which  were  in  perfect  accord  with  those  which  were 
obtained  at  the  factory,  left  little  doubt  that  the  cause  of  mischief  was 
attributable  to  the  nitro-compounds  in  the  oil  of  vitriol  used  for  gen- 
erating the  carbonic  acid  gas. 
This  conclusion  received  the  clearest  verification  at  the  hands  of  the 
manufacturer  the  instant  he  used  an  acid  that  was  free  from  smell  and 
that  did  not  respond  to  the  iron  test. 
Beyond  this  point  the  inquiry  was  not  pushed,  and,  therefore,  it  is 
not  possible  to  predict  with  certainty  the  precise  change  which  here 
takes  place.  Dr.  Thresh,  in  his  investigations  on  the  pungent  princi- 
ples of  plants,  has  demonstrated  their  ready  destructibility  under  the 
influence  of  oxidizing  agents.  And  it  is  not  improbable  that  the  effect 
produced  by  small  amounts  of  nitro-compounds,  acting  under  great 
pressure,  on  the  active  princi[)les  of  ginger  and  capsicum  is  similar  to 
