v. 
.,':> 
SPONTANEOUS  EXPLOSION  OF   PYROXYLIN.  \>  21 
^s^^r  office 
lodion,  is  a  mixture  of  two  distinct,  though  analogous  substances.  One 
is  designated  pyroxyline,  and  has  the  formula  C24    \  ?"Jf     ?  O20  assigned 
to  it  in  my  paper,  (Mem.  Chem.  Society,  iii.  p.  412;)  it  leaves  no  residuum  on 
explosion,  and  is  insoluble  in  ether.     The  other  received  the  appellation 
cotton-xyloidine,  and  the  formula  C2,,   j  TI'J      \  O20  ;  it  leaves  a  residue 
3  NO  ,  ) 
on  explosion,  is  soluble  in  ether,  &c.  The  remark  of  Mr.  Tustin,  that  his 
decomposing  gun-cotton  was  soluble  in  ether,  proves  that  it  was,  partly  at 
least,  this  latter  compound,  and  not  the  more  explosive  one.  I  shall  speak 
of  each  of  these  descriptions  of  gun-cotton  separately. 
"  Pyroxyline. — This  substance  is  produced  only  when  cotton  or  cotton- 
xyloidine,  is  immersed  in  a  mixture  of  nitric  acid,  sp.  gr.  1.5  with  strong 
oil  of  vitriol.  Although  it  contains  so  large  an  amount  of  oxide  of  nitro- 
gen, I  am  acquainted  with  no  clear  instance  in  which  it  has  undergone 
spontaneous  decomposition.  Specimens  obtained  by  the  action  of  the  mixed 
acids  on  cotton-xylodine,  have  shown  no  indications  of  change  ;  and,  py- 
roxyline obtained  in  a  compact  translucent  form  from  solution  in  acetic 
ether,  has  also  remained  unaltered. 
Cotton- Xyloidlne. — This  may  be  prepared  in  a  state  of  purity,  and  in  a 
pulverulent  condition,  by  dissolving  cottonor  pyroxylin  in  nitric  acid  of  about 
sp.  gr.  1.45,  and  precipitating  the  substance  by  water. 
Several  specimens  of  this  compound,  made  from  both  sources,  have  hith- 
erto suffered  no  decomposition,  but  they  have  been  generally  kept  in  the  dark. 
One  sample  of  precipitated  cotton-xyloidine  placed  in  a  stoppered  bottle  re- 
mained in  a  cupboard,  the  door  of  which  was  sometimes  open,  sometimes 
closed.  After  a  lapse  of  about  three  years  it  suddenly  began  to  evolve 
nitric  oxide  and  water.  The  action  continued  for  a  few  weeks  and  then 
nothing  remained  but  a  small  quantity  of  a  transparent  gummy  mass  of  a 
light  brown  color,  and  possessed  of  a  very  peculiar  odor.  Several  months 
produced  no  further  alteration.  This  product  of  decomposition  which 
had  about  the  tenacity  and  consistency  of  ordinary  gum,  was  not 
explosive :  when  heated  in  a  close  tube  per  se  it  evolved  red  fumes,  and 
afterwards  swelled  up,  being  carbonized  and  evolving  empyreumatic  oils. 
It  was  found  to  be  insoluble  in  cold  water ;  but  when  boiled  in  that  liquid 
it  swelled  up  as  a  gelatinous  mass,  and  became  disintegrated." 
After  detailing  experiments  with  a  variety  of  starchy  and  gummy  sub- 
stances, Mr.  Gladstone  remarks,  that  the  rationale  of  the  decompositions  has 
not  been  clearly  elucidated.  "  The  only  general  conclusion  which  can 
be  drawn  appears  to  be,  that  several  substances  of  the  character  above 
described,  have  a  tendency  to  suffer  spontaneous  decomposition  from 
being  oxidized  into  non-azotized  acids  at  the  expense  of  the  peroxide  of 
nitrogen  N04  they  contain,  which  is  reduced  to  the  condition  of  nitric 
oxide  N0.2  and  evolved  as  such,  a  portion  of  water  being  always  given  off 
at  the  same  time/' 
