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TANNIN  IN  BRITISH  GALLS. 
TANNIN  IN  BRITISH  GALLS. 
By  "William  Judd,  F.C.S. 
Having  noticed  for  some  three  or  four  years  past  the  large 
quantity  of  galls  on  the  oaks  in  this  neighborhood,  the  question 
naturally  occurred,  Could  not  these  galls  be  turned  to  some  practi- 
cal account  ?  When,  therefore,  this  subject  was  proposed  for  in- 
vestigation by  the  British  Pharmaceutical  Conference,  I  gladly 
undertook  to  do  what  I  could  to  set  the  matter  at  rest.  Great 
differences  of  opinion  appear  to  exist  as  to  the  value  of  these  galls, 
and  those  who  have  examined  them  have  arrived  at  very  various 
conclusions.  This  may  have  been  partly  attributable  to  the  differ- 
ent ages  of  the  galls  in  which  the  tannin  was  estimated. 
The  questions  proposed  are,  "  What  is  the  quantity  of  tannin 
in  English  galls  (Cynips  Quereus-petioli)  at  different  stages  of 
their  growth  ?  Can  they,  at  either  of  these  periods,  be  employed 
economically  as  a  substitute  for  the  nut-galls  of  commerce  ?" 
The  reply  to  the  second  question  must  obviously  depend  on  the 
results  obtained  in  investigating  the  first. 
My  first  aim  was  to  ascertain  the  most  trustworthy  and  simple 
process  for  estimating  the  quantity  of  tannin  present.  The  gela- 
tine process  being  open  to  many  objections,  I  endeavored  to  sub- 
stitute some  other.  The  plan  recommended  by  Mr.  Marriage  in 
Pharmaceutical  Journal,  vol.  iii.  p.  509,  with  ammonio-sulphate 
of  copper,  was  inadmissible  on  account  of  the  dense  color  of  the 
fluid  obtained  by  percolating  or  macerating  the  galls.  The  gallo- 
tannates  of  lead  and  antimony  are  said  by  Miller  to  be  insoluble, 
and  I  attempted  to  found  a  process  on  this  fact,  but  without  suc- 
cess. These  compounds  are  not  so  insoluble  as  stated.  Many 
other  plans  were  tried,  but  with  them  all  there  was  some  difficulty 
or  obstacle  that  rendered  the  process  useless.  I  was  obliged,  at 
last,  to  adopt  the  gelatine  process,  modified  by  the  addition  of 
alum,  as  suggested  by  Muller. 
It  is  unnecessary  to  detail  all  the  experiments  ;  suffice  it  to  say? 
the  following  results  are  the  mean  of  several  trials,  the  galls  also 
being  exhausted  in  various  ways  : — 
I.  I  first  examined  a  sample  of  old  galls,  which  had  hung  on 
the  trees  till  Christmas,  of  course  perforated  by  the  escape  of  the 
