^"'junerXt'"''}    Detection  of  Adulterations  in  Beer,  263 
To  detect  these,  one  litre  of  the  suspected  beer  is  evaporated  by  a 
moderate  heat  to  the  consistence  of  a  thick  syrup,  which  is  weighed 
in  a  glass  cylinder,  mixed  with  five  times  its  weight  of  strong  alcohol, 
whereby  gum,  dextrin,  sulphates,  phosphates  and  chlorides  are  precipi- 
tated. The  clear  liquid  is  decanted,  the  precipitate  washed  with  alcohol, 
and  the  united  filtrates  evaporated  to  a  syrupy  consistence. 
a.  A  small  portion  of  this  syrupy  residue  is  diluted  with  three  times  its 
weight  of  water  and  a  piece  of  white  woolen  macerated  in  it  for  an 
hour,  when  it  is  repeatedly  washed  with  clean  water  ;  if  picric  acid  was 
present  the  woolen  will  have  acquired  a  yellow  color,  which  cannot  be 
removed  by  washing. 
h.  The  remaining  largest  portion  of  the  syrupy  residue  is  agitated  for 
some  time  with  six  times  its  weight  of  pure,  colorless  benzol  (boiling 
point  8o°C.=i76°F.)  ;  the  operation  is  repeated,  and  the  clear  benzol 
solutions  evaporated  to  dryness.  The  pale  yellowish,  resinous  residue 
may  contain  hrucia^  strychnia^  colchicia^  or  colocynthin.  Several  small  por- 
tions of  this  residue  are  placed  upon  a  porcelain  plate  ;  to  one,  strong 
nitric  acid  is  added,  which  will  produce  a  red  color  if  brucia,  or  a  violet 
color  if  colchicia  is  present  ;  a  red  color  produced  upon  another  portion 
by  concentrated  sulphuric  acid,  indicates  colocynthin  \  and  a  purple  color 
obtained  by  bichromate  of  potassium  and  sulphuric  acid  proves  the  pres- 
ence of  strychnia.  If  none  of  these  colorations  have  been  produced, 
the  resinous  residue  obtained  as  above  will  have  the  well-known  bitter 
taste  of  hops  ;  otherwise  this  will  be  modified  bv  the  taste  of  the 
principles  mentioned. 
c.  The  syrupy  residue  above  is  freed  from  benzol  by  a  moderate  heat, 
and  then  twice  agitated  with  pure,  colorless  amylic  alcohol  of  132^0. 
(267°  F.)  boiling  point.  The  first  portion  of  the  amylic  alcohol  will 
have  acquired  a  lighter  or  darker  wine  or  golden-yellow  color  ;  also,  a 
strongly  bitter  taste  if  picrotoxin  or  aloes  are  present.  The  bitter  princi- 
ples of  hops,  wormwood,  gentian,  bogbean  and  quassia,  are  not  soluble 
in  this  solvent.  A  portion  of  the  bitter  amylic  alcohol  is  evaporated 
spontaneously  from  a  glass  plate,  when  picrotoxin  will  separate  in  white 
crystals,  and  aloes  may  be  recognized  by  the  peculiar  safFron-like  color. 
d.  A  piece  of  filtering-paper  will  absorb  the  last  portions  of  fusel 
oil  from  the  syrupy  residue,  which  is  then  agitated  with  ether.  This 
solvent  removes  the  remaining  hop  bitter,  and  will  also  dissolve  a/?sint/?iin^ 
if  present.  The  ether  being  evaporated,  the  absinthiin  is  recognized  by 
the  peculiar  odor  of  wormwood  and  by  the  reddish-yellow  coloration, 
changing  to  indigo-blue  on  the  addition  of  sulphuric  acid. 
