ON  THE  OIL  OF  HOPS. 
443 
properties  of  oil  of  hops.  It  has  been  believed,  in  consequence  of 
this  examination,  that  the  oil  resembled  oils  of  mustard,  assafce- 
tida,  &c,  and  belonged  to  the  ethereal  oils  containing  sulphur; 
that  it  dissolved  largely  in  water,  and  on  this  account  preserved 
the  beer,  and  that  it  acted  partly  as  the  narcotic  ingredient  of 
beer  and  of  hops. 
The  following  research  conducted  by  me  with  oil  carefully  pre- 
pared by  Hertel,  shows  that  the  deductions  of  Payen  and  Cheval- 
lier  are  incorrect.  The  oil  wTas  distilled  from  fresh  hops  with 
water,  and  constituted  about  8  per  cent,  of  the  hops,  which  were 
dried  in  the  air.  It  was  of  a  clear  brownish  yellow  color,  possessed 
a  strong  odor  of  hops,  and  had  a  slightly  bitter  taste  analogous  to 
thyme  and  origanum.  Its  specific  gravity  was  *908  at  61°  Fahr. 
It  scarcely  reddened  litmus  paper,  which,  when  moistened  with 
the  oil  and  exposed  to  the  atmosphere  for  a  considerable  time, 
assumed  a  decisive  red  color.  A  small  quantity  shaken  with 
water  dissolved  in  such  a  small  degree  that  the  water  only  had  the 
odor  of  the  oil.  It  requires  more  than  600  times  its  weight  of 
water  for  its  solution. 
It  was  examined  for  the  purpose  of  ascertaining  whether  it 
contained  sulphur,  but  with  a  negative  result.  The  oil  rendered 
anhydrous  by  distillation  over  fused  chloride  of  calcium,  evaporates 
partly  at  a  temperature  below  the  boiling  point  of  water.  It 
begins  to  boil  at  257°,  the  boiling  then  rises  to  347°,  where  it 
remains  stationary  for  some  time,  and  at  which  nearly  one-sixth  of 
the  oil  distils  over.  The  first  distillate  (A)  was  colorless,  clear 
as  water,  and  possessed  a  slight  odor  of  hops,  but  more  resembled 
rosemary.  The  portion  (B)  passing  over  between  347°  and  437°, 
and  constituting  one-half  of  the  oil,  was  also  very  clear,  and  had 
the  odor  of  the  crude  oil.  That  which  passed  over  between  437° 
and  455°  was  colored  yellowish.  The  residue  in  the  retort,  abou* 
one-sixth  of  the  oil,  was  brownish  and  like  turpentine.  It  is, 
therefore,  evident  that  oil  of  hops  is  a  mixture  of  oils.  The  crude 
oil  did  not  give,  with  an  ammoniacal  solution  of  silver,  a  metallic 
mirror.  It  is  not,  therefore,  an  aldehyde.  When  mixed  with  an 
alcoholic  solution  of  potash  the  oil  becomes  brown,  and  by  distil- 
lation the  mixture  affords  alcohol  and  an  oil  with  the  odor  of 
rosemary.  After  the  greatest  part  of  the  oil  and  spirit  has  dis- 
tilled over,  a  violent  evolution  of  gas  ensues,  probably  hydrogen, 
