ON  THE  CHEMICAL  HISTORY  OP  LUPULIN.  27 
pidly  acidifies.  Treated  by  potassa,  it  becomes  brown  and  resin- 
ous ;  it  reduces  the  nitrate  of  silver  with  the  greatest  facility, 
and  is  transformed  into  valerianic  acid,  without  the  production 
of  resin,  by  chromic  acid.  All  these  properties  designate  this  body 
as  an  aldehyde,  and  analysis  has  proved  that  it  is  the  aldehyd 
of  valerianic  acid,  with  the  formula)  C10  H10  II2- 
M.  Personne  found  no  trace  of  sulphur  in  the  oil  of  hops. 
Fixed  principles  of  Lupulin. — On  examining  the  residue  of 
the  lupulin  after  distillation  the  author  found  but  two  substances 
to  merit  special  notice — a  complex  resinous  substance  and  a  bit- 
ter principle. 
The  resinous  matter  of  Lupulin  is  difficult  to  obtain  in  a  pure 
state.  The  residue  noticed  before,  is  boiled  with  water  in  suc- 
cessive quantities,  till  the  bitter  principle  and  as  much  of  the 
acid  as  possible  is  removed  ;  it  is  then  boiled  in  alcohol  until  all 
but  the  cellulose  of  the  lupulin  grains  is  dissolved.  The  hot 
alcoholic  solution  deposits  a  species  of  wax  by  cooling.  The 
cold  alcoholic  liquor  by  evaporation  yields  the  resinous  matter. 
As  thus  obtained  it  yet  retains  a  little  volatile  oil  and  valerianic 
acid.  It  softens  by  the  heat  of  the  hand,  has  a  yellow  color 
varying  from  a  golden  yellow  to  deep  orange,  according  to  its 
age  and  exposure  ;  after  long  exposure  to  the  air  it  obstinately 
retains  the  odor  of  hops.  It  is  slightly  soluble  in  water  and 
communicates  to  it  the  property  of  frothing  by  agitation.  Cold 
solutions  of  potassa  and  ammonia  dissolve  the  larger  portion  of 
it  and  separate  a  resin  insoluble  in  these  alkalies,  but  soluble  in 
alcohol,  and  which  is  dry,  friable,  and  odorless.  When  the  al- 
kaline solution  is  saturated  with  sulphuric  acid  the  resin  is  pre- 
cipitated free  from  valerianic  acid. 
This  substance  should  not  be  considered  a  true  resin  but  is  a 
product,  intermediate  between  resin  and  volatile  oil.  It  com- 
poses two  thirds  of  the  weight  of  the  lupulin  of  commerce. 
Ihe  bitter  principle — which  the  author  calls  Lapuline — exists 
in  the  aqueous  decoction  of  lupulin,  and  appears  to  belong  to 
the  class  of  alkaloids  and  contains  nitrogen.  After  many  at- 
tempts in  which  means  of  the  most  varied  character  were  em- 
ployed he  was  unsuccessful  in  isolating  this  principle  in  a  state 
of  purity,  yet  he  has  approached  sufficiently  near  to  form  an 
opinion  of  its  nature.    It  is  readily  precipitated  by  tannic  acid, 
