236  Tannin  in  Quercus  Alba.  {^'^vm*™' 
the  identity  of  the  crystalline  principle  extracted  by  petroleum  ether 
with  that  obtained  by  Lloyd  from  the  same  species.  They  are 
alike  in  chemical  and  physical  properties.  Combustions  of  the  last 
substance  have  as  yet  not  bsen  made.  It  was  also  noticed  that  the 
northern  bark  contains  its  peculiar  principle  much  more  abundantly 
than  the  southern. 
The  fixed  oil  obtained  appears  to  be  a  sulphurated  compound. 
A  portion  saponified  with  KOH  and  subsequently  acidified  with  dilute 
HC1  gave  decided  evidence  of  H2S.  Nitric  acid  acts  energetically 
upon  the  oil,  producing  elaidin.  The  aqueous  and  acid  filtrate  from 
this  gives  a  precipitate  with  barium  chloride  insoluble  in  nitric  or 
hydrochloric  acids. 
TANNIN  OF  QUERCUS  ALBA.1 
By  Henry  Kraemer,  Ph.G. 
One  of  the  most  abundant  and  interesting  principles,  produced 
during  the  life  of  numerous  trees  and  herbs,  and  more  especially  in 
the  barks  and  leaves  of  such,  is  a  vegetable  acid  of  astringent  taste, 
giving  blue  or  green  compounds  with  salts  of  iron  and  by  reason  of 
its  use,  from  many  sources,  in  the  process  of  making  leather  is 
called  "tannin."  The  constitution  of  but  one  tannin,  that  of  nut- 
galls  is  thus  far  understood.  There  are  nevertheless  several  import- 
ant classes  of  tannins  recognized,  based  upon  derivatives  obtained 
from  them;  those  which  yield  on  dry  sublimation  either  pyrogallic 
or  pyrocatechuic  acids;  and  those  giving  upon  fusion  with  potas- 
sium hydroxide  either  protocatechuic  acid  or  phloroglucol.  Upon 
the  suggestion  of  Prof.  John  M.  Maisch,  I  have  undertaken  the 
study  of  the  tannin  of  our  officinal  "White  Oak  Bark;"  and  to  him 
I  am  indebted  for  references  and  many  valuable  suggestions  in  this 
work. 
The  preparation  of  a  pure  tannin  is  attended  with  considerable 
difficulty.  The  process  which  was  found  most  practicable,  was  to 
macerate  about  2^  kilos  of  Quercus  alba"  with  95  per  cent,  of 
alcohol  for  a  few  days ;  then  to  pack  in  a  percolator  and  allow  per- 
1  This  paper  is  an  abstract  of  the  chemical  work  reported  in  the  author's 
thesis  a  year  ago,  to  which,  at  the  editor's  request,  some  investigations  more 
recently  made  have  been  added.  The  histological  work,  reported  in  the 
author's  thesis,  has  not  yet  been  arranged  for  publication. — Editor  Amer. 
Jour.  Phar. 
