ON  THE  PREPARATION  OF  COLLODION. 
213 
the  peroxide  displaces  one  equivalent  of  hydrogen  from  the  cotton, 
forming  soluble  cotton,  while  the  hydrogen  combines  with  the 
equivalent  of  oxygen  from  the  nitric  acid,  forming  one  of  water. 
The  change  expressed  in  symbols  will  render  it  more  simple  : 
C12H10O10+N,O5=C12(H9NO4)O10+H,O. 
When  the  nitro-sulphuric  acid  is  too  strong,  and  the  cotton 
remains  in  for  some  time,  it  is  thought  to  have  been  combined 
with  two  equivalents  of  the  peroxide  ;  thus  rendering  the  cotton 
insoluble  and  very  explosive.  My  experience  has  forced  me  to 
believe  that,  instead  of  there  being  only  two  varieties,  the  soluble 
and  the  insoluble,  or  explosive,  there  are  varieties  of  every  degree 
of  solubility,  from  the  perfectly  soluble  to  the  entirely  insoluble. 
This  difference  in  solubility  is  due,  probably,  to  the  cotton  not 
being  properly  acted  upon,  and  at  improper  temperatures. 
I  have  made  the  following  experiments  to  show  the  different 
textures  and  solubilities  resulting  with  nitro-sulphuric  acid  of 
different  strengths : 
Experiment  1st. —  To  half  a  fluid  ounce,  each,  of  commercial 
sulphuric  acid  and  fuming  nitric  acid,  sp.  gr.  145,  mixed,  was 
added  30  grains  of  finely  carded  cotton,  which,  after  remaining 
in  the  mixture  for  ten  minutes,  was  taken  out  and  washed 
thoroughly  with  an  abundance  of  water,  until  no  acid  was  per- 
ceptible. The  fibre  of  this  cotton  was  strong  and  perfect,  with- 
out being  matted,  and  washing  with  ease.  After  picking  apart, 
drying,  and  again  weighing,  I  found  it  had  gained  17  grains,  or 
56f  per  cent.  ;  it  was  partially  soluble  in  ether,  or  a  mixture  of 
ether  and  strong  alcohol,  in  the  proportion  of  5  parts  of  the 
former  to  3  of  the  latter,  the  insoluble  portion  settling  to  the 
bottom  in  a  semi-gelatinous  form.  A  small  portion  of  the  alco- 
hol and  ether  solution,  dropped  upon  glass,  spread  evenly  and 
dried  into  an  adhesive,  transparent  film.  This  variety  is  slightly 
explosive,  leaving  a  trace  of  carbonaceous  substance.  The  tem- 
perature of  the  acids,  before  mixing,  was  74°;  after,  120°  F. 
Experiment  2nd — To  the  same  quantity  of  sulphuric  acid,  as 
in  experiment  1st,  was  added  a  mixture  of  three  drachms  of 
fuming  nitric  acid  and  one  of  water  ;  the  temperature  now  rose 
from  74°  to  158^  F.  To  this  mixture,  30  grains  of  cotton  was 
added,  and  at  the  end  of  ten  minutes  was  taken  out,  and  found 
to  wash  with  much  difficulty,  being  much  matted,  and  having  a 
