VARIETIES. 
465 
laboratory,  to  various  substances.    Several  bodies  which  furnish 
crystallized  sugar  when  treated  with  dilute  acids  with  the  aid  of 
heat?  also  furnished  this  sugar  when  treated  in  this  way  with 
alkalies  ;  thus,  for  example,  a  yellow  crystallized  substance  from 
twigs  of  Thuja  occidentalis  may  be  decomposed  by  alkalies,  as 
also  by  acids,  in  hydrogen  gas,  into  well-crystallized  grape- 
sugar,  and  a  yellow  crystalline  body,  similar  to  quercetine,  which 
acquires  a  beautiful  bluish-green  color  with  ammonia.  The 
author  has  also  induced  Kawalier  to  submit  the  tannin  of  galls 
to  this  treatment.    In  this  way  is  obtained  gallic  acid,  which 
may  easily  be  procured  pure  by  this  process,  and  an  amorphous 
yellowish  body,  of  a  somewhat  bitter  and  acid  taste,  similar  to 
gum-arabic,  which  on  analysis  gave  numbers  corresponding  with 
the  formula  C12  H11  O11.    From  about  150  grms.  of  tannin,  not 
1  milligrm.  of  sugar  was  formed.    The  fluid  freed  from  gallic 
acid  reduced  no  trace  of  protoxide  of  copper  from  Fehling's 
fluid.    Further  experiments,  which  Kawalier  has-  commenced 
with  larger  quantities  of  tannin,  will  serve  to  determine  the  atomic 
weight  of  the  amorphous  body. —  Ohem.  Graz.  June  15,  1857, 
from  Sitzungsber.  der  AJcad.  der  Wiss.  zu  Wien. 
The  Gums  and  Resins  of  Commerce.    By  P.  L.  Simmonds. 
(Concluded  from  pago  379.) 
A  resinous  gum  called  Alkor  Lek  (whence  the  word  lac),  flows  from 
the  Pistacia  Terebinthus,  Linn.,  in  Algeria,  which,  mixed  with  other  ingre- 
dients, is  given  as  a  purgative  for  fowls.  It  is  supposed  that  this  tree 
would  yield  good  terebinthine.  The  gum  flows  so  abundantly,  even  with- 
out incision,  that  it  is  often  dangerous  to  sleep  under  the  trees. 
Under  the  commercial  name  of  Dragon's  Blood,  the  produce  of  several 
species  of  Dracaena  is  imported  to  the  extent  of  about  100  packages  of  1 
to  2  cwts.  each.  In  commerce  the  resin  occurs  in  powder,  grains,  masses, 
drops  of  the  size  of  an  olive,  and  in  sticks  enveloped  in  the  leaf  of  the 
talipot  palm.  Its  chief  use  is  for  coloring  artificial  tortoise-shell,  and  in 
paints,  varnishes,  sealing-wax,  &c.  It  stains  marble,  especially  if  the 
stone  be  heated.  The  resin  is  used  occasionally  in  medicine  as  a  tonic 
and  astringent,  and  also  in  opiates  and  dentifrices.  Occasionally  a  brick 
red  powder,  known  in  the  East  as  wurrus,  has  been  passed  off  here  for  dra- 
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