584  Some  Constituents  of  Hops.  { Am^-I8^rm' 
estimated  by  means  of  a  standardized  solution  of  gelatin  containing 
alum ;  only  about  6  per  cent,  of  tannin  could  be  found.  The 
remainder  of  the  solution  was  then  precipitated  with  neutral  acetate 
and  with  subacetate  of  lead  ;  the  two  precipitates  had  much  the  same 
appearance,  and  both  were  soluble  in  acetic  acid.  They  were  each 
thoroughly  washed,  then  suspended  in  water  and  decomposed  with  sul- 
phuretted hydrogen.  The  filtrate  from  each  was  found  to  contain  the 
tannin,  which  gave  a  blackish-green  color  with  ferric  chloride,  and  pre- 
cipitated a  solution  of  gelatin  containing  alum.  The  two  solutions 
were  mixed  and  the  tannin  precipitated  with  an  excess  of  common  salt, 
from  which  an  unsuccessful  attempt  was  made  to  entirely  free  it. 
For  the  final  experiment  six  ounces  of  hops  were  taken  and  exhausted 
with  boiling  water ;  the  decoction  was  concentrated,  treated  with  alcohol, 
filtered,  the  alcohol  evaporated  off,  the  residue  dissolved  in  water,  and  the 
percentage  of  tannin  estimated  as  before  ;  only  a  little  more  than  ^0  per 
cent,  being  found.  The  solution,  being  acid  to  test  paper,  was  carefully 
neutralized  with  ammonia  and  precipitated  with  neutral  acetate  of  lead, 
a  bright  yellow  precipitate  being  obtained  ;  the  filtrate  gave  no  reaction 
with  subacetate  of  lead  and  contained  no  tannin.  The  precipitate  was 
thoroughly  washed,  suspended  in  water,  decomposed  with  sulphuretted 
hydrogen,  the  precipitate  washed  until  the  washings  gave  no  color  with 
ferric  chloride,  and  the  filtrate  evaporated  to  a  small  bulk,  and  shaken 
with  ether  in  hopes  that  the  tannin  might  be  dissolved  ;  the  ether, 
however,  failed  to  take  up  any  of  the  tannin,  and  portions  of  the  solu- 
tion were  therefore  treated  with  the  following  reagents  :  tartar  emetic, 
which  produced  a  nearly  white  precipitate  on  standing  ;  ferrous  sul- 
phate, no  effect ;  sulphuric  and  hydrochloric  acids  at  once  produced 
precipitates  ;  protochloride  of  tin,  no  effect  ;  sulphate  of  copper,  no 
effect  ;  solution  of  potassa  gave  a  dark  reddish-brown  color,  but  no 
precipitate  ;  gelatin  gave  a  precipitate  on  standing.  The  green-black 
precipitate  with  ferric  chloride  certainly  indicates  that  this  is  not  gallo- 
tannic  acid,  which  in  other  respects  it  resembles,  and  the  reaction  with 
the  mineral  acids  would  seem  to  show  with  equal  certainty  that  the, 
tannin  is  not  moritannic  acid,  which  it  is  stated  by  Wagner  to  resemble. 
