632  Extraction  of  Tanning  Materials.      {ADwimbe£i£f ' 
affected  by  the  temperature,  97  per  cent,  of  the  total  color  being 
extracted  by  cold  water,  and  the  lowest  amount  of  color  in  propor- 
tion to  tanning  matter  being  obtained  at  about  400. 
Smyrna  valonia  behaves  in  rather  a  peculiar  manner.  On  increas- 
ing the  temperature  from  150  to  400,  the  non-tannins  were  found  to 
steadily  decrease  with  a  corresponding  increase  in  the  tannins,  which 
points  to  a  probable  transformation  of  some  anhydrides  or  gluco- 
sides  into  tannin.  50°-6o°  appears  to  be  the  best  temperature 
for  the  extraction  of  this  material,  as  at  higher  temperatures  the 
proportion  of  color  increases,  and  the  tannin  decreases.  As  would 
naturally  be  expected,  the  Greek  valonia  behaves  in  a  very  similar 
way  to  the  Smyrna,  and  gives  the  best  results  between  6o°  and  700. 
It,  however,  gives  off  its  tannin  more  quickly  than  the  Smyrna 
beard. 
The  maximum  yield  of  tanning  matter  from  sumach  was  found 
to  be  obtained  at  50°-6o°,  while  Messrs.  Seymour,  Jones  and 
Palmer,  who  first  drew  attention  to  the  matter,  found  it  between  300 
and  400,  a  result  which  was  confirmed  by  Mr.  J.  T.  Wood.  This 
difference  may  be  due  either  to  some  peculiarity  in  our  sample  or  to 
a  difference  in  the  manner  of  experimenting,  and  needs  further 
inquiry.  It  seems  probable,  from  the  increase  in  non-tannins,  cor- 
responding to  the  diminished  yield  of  tannin  at  higher  temperatures, 
that  some  actual  decomposition  takes  places.  The  extractions 
made  over  6o°  were  extremely  difficult  to  filter,  and,  on  standing, 
continued  to  deposit,  whereas  those  extracted  at  a  lower  tempera- 
ture remained  quite  clear. 
It  will  be  noted  that,  even  in  the  case  of  quebracho  wood,  where 
heat  is  essential  to  good  extraction,  the  maximum  yield  of  tannin 
is  obtained  below  ioo°,  while  the  color  increases  by  over  25  per 
cent,  between  900  and  ioo°.  It  is  highly  probable  that  in  this  case 
there  is  an  actual  conversion  of  some  of  the  tannins  into  red  anhy- 
drides, similar  to  that  which  has  been  observed  in  other  catechol 
tannins. 
In  the  case  of  mangrove  bark,  the  maximum  yield  of  tannin  is 
practically  reached  at  6o°,  while  beyond  this  the  tannin  remains 
nearly  steady,  and  the  color  increases  very  irregularly  up  to  100°. 
It  was  noted  that  above  400  the  infusions  became  turbid  on  cooling, 
through  deposits  of  difficultly  soluble  reds,  and  that  over  6o°  they 
became  very  difficult  to  filter. 
