106 
NOTE  ON  COLLODION. 
it  is  quite  evident  that  the  physical  property  of  the  resulting 
compound,  as  regards  solubility  in  alcoholic  ether,  is  exceedingly 
variable  and  it  would  be  interesting  to  know  whether  these  de- 
grees of  solubility  are  parallel  with  the  proportion  of  NO5 
absorbed  into  the  constitution  of  the  cotton.  When  fully 
nitricised,  100  parts  became  169.5  parts  of  gun-cotton  fit  for 
blasting.  In  my  experience  with  the  Pharmacopoeia  process  100 
parts  became  usually  125  parts.  Last  autumn,  when  illus- 
trating this  subject  to  the  class,  cotton  was  immersed  in 
equal  parts  of  commercial  sulphuric  acid  and  red  fuming 
nitric  acid  sp.  gr.  1.45  and  then  set  aside  until  the  next  lecture, 
an  interval  of  four  days  elapsing,  when  it  was  removed,  washed, 
pressed,  washed  in  alcohol,  again  pressed,  and  was  found  to  be 
completely  soluble  in  alcoholic  ether  without  residue.  Since 
then  I  have  repeatedly  tried  the  process  with  the  long  maceration 
and  have  uniformly  succeeded  in  obtaining  a  soluble  cotton,  and 
now  offer  the  following  formula  based  on  this  experience. 
Take  of  Fuming  nitric  acid,  (sp.  gr.  1.42  to  145) 
Sulphuric  acid,  of  each  four  fluid  ounces. 
Cotton,  free  from  impurities        half  an  ounce. 
Commercial  ether  two  and  a  half  pints. 
Alcohol  and  water,  of  each  a  sufficient  quantity. 
Mix  the  acids  in  a  suitable  vessel  capable  of  being  covered; 
introduce  the  cotton,  and  after  pressing  it  into  the  acid  until 
perfectly  immersed  and  saturated,  allow  it  to  stand  four  days. 
The  cotton  should  then  be  removed,  the  excess  of  acid  pressed 
out,  and  then  thoroughly  washed  till  it  is  neutral  to  litmus  paper. 
It  should  now  be  strongly  pressed  between  bibulous  paper,  then 
immersed  in  strong  alcohol  to  abstract  the  adherent  water,  and 
again  pressed,  when  it  may,  without  further  drying,  be  put  in 
the  ether  and  dissolved.  The  use  of  alcohol  for  drying  gun-cotton 
is  an  improvement  attributed  to  the  late  W.  W.  D.  Livermore  of 
Philadelphia. 
The  collodion  by  this  process  is  less  mucilaginous  than  that 
obtained  by  the  U.  S.  P.  formula,  but  it  is  very  adhesive  and 
dries  rapidly.  There  is  no  necessity  of  teasing  the  cotton  about 
in  the  acid  mixture  with  glass  rods,  when  so  much  time  is 
afforded  for  the  maceration,  and  hence  the  fibres  of  the  cotton 
are  less  interwoven  and  can  be  separated  readily  when  picked 
out  previous  to  drying,  when  it  is  desired  to  get  it  in  that  state. 
