622  Nitration  of  Cellulose.  { ^"DeZisJi!""' 
states  that  the  failure  in  obtaining  a  good  ointment  is  not  due  to  the 
presence  of  salt  in  the  lard,  or  of  lead  in  the  mercury,  and  tliat  oint- 
ment spoiled  by  keeping  may  be  restored  by  warming  with  nitric  acid, 
thus  indicating  that  nitric  acid  is  essential  to  its  preservation,  and  that 
by  keeping  some  of  the  acid  is  lost. 
But  in  the  ^'  Pharmaceutical  Journal [3],  vol.  vi,  p.  708,  in  a  paper 
by  Mr.  Fredigke,  of  Chicago,  it  is  stated  that  a  superior  <  (intment  both 
in  appearance  and  in  durability  may  be  prepared  by  oxidizing  the  fat 
by  nitric  acid,  previous  to  adding  the  mercurial  solution.  This  would 
seem  to  show  that  the  oxidized  fat  forms  a  compound  with  the  mercuric 
nitrate,  the  color  being  due  to  the  elaidin  formed  by  reaction  of  fat  and 
acid. 
Such,  then,  are  the  results  of  their  experiments ;  but  as  they  are  to  a 
great  extent  conflicting,  it  is  impossible  to  arrive  at  any  definite  conclu- 
sions without  experimental  research,  and  pressure  of  time  debarred  me 
from  such  a  course,  so  that  I  have  been  obliged  to  leave  the  subject 
with  this  historical  sketch. — Phar.  Jour,  and  Trans.,  Nov.  4,  1882. 
NITRATION  OF  CELLULOSE. 
By  Vieili.e. 
The  cellulose  used  was  in  the  form  of  cotton-wool.  The  lowest 
nitration  product,  mononitro-cellulose,  is  obtained  by  the  action  of 
nitric  acid  of  sp.  gr.  1*450.  It  is  insoluble  in  ethyl  acetate  and  in  a 
mixture  of  alcohol  and  ether  :  analyzed  by  Schloesing's  method,  1  gram 
yields  108 '9  cc.  of  nitric  oxide.  A  nitration  product,  soluble  in  a 
mixture  of  alcohol  and  ether,  and  therefore  suitable  for  making  collo- 
dion, is  given  only  by  acid  of  sp.  gr.  between  1"49P  and  1*496.  It 
retains  the  structure  of  the  original  cotton,  and  is  entirely  soluble  in 
ethyl  acetate ;  1  gram  yields  183  to  194'4  cc.  of  nitric  oxide.  The  time 
required  to  produce  the  maximum  nitration  with  acid  of  a  particular 
strength  is  longer  the  weaker  the  acid,  2  to  3  hours  sutficiilg  with  acid 
of  sp.  gr.  1'50,  whilst  acid  of  1*483  requires  120  hours.  With  acid  of 
sp.  gr.  1*470,  however,  the  cotton  swells  up  and  dissolves  immediately, 
and  under  these  conditions  nitration  is  rapid  ;  when  the  syrupy  solu- 
tion is  poured  into  water,  a  white  precipitate,  which  has  none  of  the 
structure  of  the  original  cotton,  is  thrown  down.  Acid  of  sp.  gr.  1*46Q 
acts  only  slowly  on  cotton,  but  the  fibres  become  very  brittle,  and  the 
