402  SPONTANEOUS  DECOMPOSITION  OF  PYROXYLIN. 
Now  the  2*352  grms.  of  gun  cotton  mentioned  have  given  : — 
Grms. 
Water  and  nitrous  vapors  from  212°  to  230°  0-791 
Matter  soluble  in  ether  0.009 
Matter  soluble  in  alcohol  0-210 
Matter  soluble  in  water  1-227 
Matter  insoluble  in  water  and  alcohol  0-070 
Loss  0045 
2-352 
It  results  from  these  numbers  that  the  modified  gun  cotton, 
after  being  dried  at  230°  F.,  yields  to  alcohol  14  per  cent,  of 
its  weight,  and  to  water  78  per  cent.  ;  that  is  to  say,  nearly  the 
whole  of  the  dry  matter,  consequently  it  follows  that  gun  cotton, 
which  is  insoluble  in  water  and  alcohol,  in  decomposing  spon- 
taneously, can,  under  the  influence  of  the  nitrous  vapors  which  it 
disengages,  give  rise  to  products  neutral  and  acid,  soluble  in 
water  and  in  alcohol,  and  which  the  author  is  engaged  with  at 
this  time. 
When  the  aqueous  solution  of  the  altered  cotton  is  evaporated 
on  a  water  bath,  a  substance  is  obtained,  which  swells  in  volume 
and  becomes  spongy  towards  the  end  of  the  evaporation.  This 
substance  is  light,  white,  friable  internally,  but  adhesive  where  in 
contact  with  the  air,  owing  to  its  hygroscopic  tendency.  This 
matter  is  spongy,  it  is  not  soluble  in  ether,  to  which,  neverthe- 
less, it  communicates  a  slight  acidity  ;  neither  is  it  soluble  in  a 
mixture  of  alcohol  and  ether,  but  it  is  partially  soluble  in  al- 
cohol. The  matter  dissolved  by  the  alcohol  reduces  easily  and 
abundantly  the  tartrate  of  copper  and  potassa  ;  the  insoluble 
portion  left  in  contact  with  moist  air  during  24  hours,  assumes 
the  appearance  of  a  dense  solution  of  gum. 
The  aqueous  solution  of  altered  gun  cotton,  when  mixed  with 
eight  times  its  volume  of  alcohol,  gives  an  abundant  flocculent 
precipitate,  which,  when  washed  on  a  filter  with  alcohol  and  dried 
over  sulphuric  acid,  is  amorphous,  nearly  opaque,  friable  and 
with  a  gummy  appearance.  It  dissolves  easily  in  cold  water, 
and  the  solution  is  precipitated  by  acetate  of  lead. 
Altered  gun  cotton  is  attacked  by  hot  nitric  acid  with  the 
evolution  of  nitrous  vapors,  and  the  production  of  matters  solu- 
ble in  water,  and  precipitable  by  the  salts  of  lead,  silver  and 
mercury. 
