Am.  Jour.  Pharm."! 
August,  1884.  j 
Bitter  Substance  of  Hops. 
429 
four  or  five  crystallizations.  The  mother  solutions  must  be  speedily 
evaporated  if  we  still  wish  to  obtain  crystals ;  after  a  time  they  will 
only  furnish  a  resinous  residue. 
The  hop-bitter  acid  melts  at  92°  to  93°.  It  is  easily  soluble  in 
alcohol,  ether,  benzol,  chloroform,  sulphide  of  carbon  and  vinegar ;  to 
a  lesser  extent  in  cold  petroleum  ether,  and  not  at  all  in  water. 
In  the  analysis  I  obtained  figures  which  correspond  best  with  those 
calculated  from  the  formula  C25H3504. 
Obtained. 
Calculated.  ,  ■  , 
,  '  ,  2.  Crystal.        3.  Crystal.       5.  Crystal.         6.  Crystal. 
p.  c.         p.  c.         p.  c.        p.  c.  p.  c.  9      p.  c.         p.  c. 
C  75-19       74-79       74'83       74*9        75*04       75'05  75-07 
H         8-77        8-97      .  8'90        8'85        8"87        8*83  8'80 
O  16-04 
If  we  shake  up  the  other  solution  of  bitter  substance  with  an  aque- 
ous solution  of  acetate  of  copper,  the  ether  will  assume  a  green  color, 
and  gradually  deposits  a  green  crystalline  powder,  a  cupreous  combi- 
nation of  the  bitter  acid.  It  is  difficult  to  obtain  in  a  pure  state,  as 
the  solutions  are  already  subject  to  slight  decomposition,  accompanied 
by  a  small  deposit  of  copper  oxide.  This  combination  is  readily  solu- 
ble in  alcohol,  to  a  lesser  extent  in  ether,  and  is  insoluble  in  water. 
In  the  course  of  analysis  I  obtained  the  following  figures  : 
C   69-4  per  cent.      69-3  per  cent. 
H.   7*95       "  7-98  " 
OU   7-20       "  7-18 
If  we  suppose  that  the  copper  combines  with  two  molecules  of  hop- 
bitter  acid,  by  the  decomposition  of  one  of  its  atoms,  H,  we  obtain  the 
formula  C50H68O8  Cu.  This  combination  will  contain  69*87  per  cent. 
C,  7*91  per  cent.  H  and  7'33  per  cent.  Cu.  The  figures  obtained  do 
not  perfectly  coincide  with  those  calculated ;  it  is  nevertheless  probable 
that  the  formula  is  correct,  and  the  combined  substance  analyzed  was 
not  perfectly  true. 
I  have  already  referred  to  the  fact  that  solutions  of  hop-bitter  acid, 
if  left  standing  too  long,  assume  a  yellow  color,  and  on  evaporation 
leave  only  a  yellow  resinous  residue.  This,  as  its  reaction  shows, 
evinces  a  complete  analogy  with  the  crystallized  acid.  The  dark  col- 
ored mother  solution,  from  which  the  crystalline  cakes  of  bitter  acid 
are  obtained,  contains  a  large  proportion  of  this  resinous  compound, 
