568 
Colloidal  Cellulose. 
Am.  Jour.  Pharm. 
Nov.,  1889. 
which  assimilate  carbonic  anhydride  without  ever  producing  tannin  ; 
and  oak,  willow,  and  alder  leaves  assimilate  in  dull  weather  without 
the  amount  of  tannin  being  increased.  The  tannin  produced  in  the 
leaves  passes  into  the  branches  and  roots,  and  there  is  no  experimental 
evidence  to  show  that  the  tannin  which  has  once  passed  into  the  rhi- 
zome undergoes  further  change ;  there  is  rather  an  increase  in  the 
amount  of  tannin  in  the  rhizome  through  a  production  in  the  dark. 
With  regard  to  the  use  of  tannin  to  leaves,  the  author  is  inclined  to 
view  it  as  a  protecting  agent  either  to  prevent  the  plant  from  being 
eaten  or  to  prevent  rotting,  etc. 
Falling  leaves  contain  as  much  tannin  as  they  did  during  their  best 
time  of  growth,  indicating  that  the  leaf  tannin  is  of  no  value  to  the 
plant. 
During  germination  in  the  dark  of  seeds  containing  tannin  (such  as 
the  seeds  of  oak  and  horse-chestnuts)  there  is  no  "diminution,  but  an 
increase  in  the  amount  of  tannin. 
There  is  not  yet  sufficient  evidence  to  show  whether  tannin  is  pro- 
duced from  non-nitrogenous  substances,  or  whether  it  is  formed  in  the 
conversion  of  nitrogenous  compounds  into  albuminoids.  It  seems 
probable  that  aromatic  compounds  may  be  formed  in  the  production 
of  albumin,  some  of  which  are  used  in  the  building  up  of  albumin 
molecules,  whilst  others  yield  tannin. 
COLLOIDAL  CELLULOSE.1 
By  C.  E.  Guignet. 
Filter-paper  previously  treated  with  hydrochloric  and  hydrofluoric 
acids,  or  carded  cotton  of  the  finest  quality,  is  carefully  dried  and 
immersed  in  sulphuric  acid  of  50°  B.,  care  being  taken  to  avoid  a  rise 
of  temperature.  The  cellulose  forms  a  transparent,  gelatinous  mass, 
which  is  not  affected  by  contact  with  a  large  excess  of  acid,  but  is  rap- 
idly converted  into  dextrin  at  100°.  When  the  acid  has  been  com- 
pletely removed  by  washing,  the  colloidal  cellulose  dissolves  in  pure 
water.  In  order  to  ensure  complete  removal  of  the  acid,  it  is  advis- 
able to  finish  the  washing  with  alcohol,  and  it  is  then  dried  at  the 
lowest  possible  temperature. 
Colloidal  cellulose  forms  with  water  a  slightly  milky  solution, 
1  Compt.  rend.,  cviii,  1258 — 1259 ;  reprinted  from  Jour.  Chem.  Soc,  1889, 
p.  847, 
