20 
SPONTANEOUS  DECOMPOSITION  OF  PYROXYLIN. 
from  the  disposition  which  it  shows  for  undergoing  spontaneous 
decomposition,  great  care  ought  to  be  exercised  whenever  this  ar- 
ticle is  intended  to  keep  for  any  length  of  time.  "Wrapping  it  in 
paper,  for  instance,  and  laying  it  along  side  of  other  parcels,  would 
in  my  opinion  be  incurring  the  risk  of  great  mischief  and  danger, 
from  the  liberation  of  the  free  nitrous  acid  gas- 
James  Beatson,  Apothecary, 
U.  S.  Naval  Hospital. 
United  States  Naval  Hospital,  New  York  Station,  Sept.  1851. 
Note  by  the  Editor. — We  have  also  noticed  the  decomposition  of  gun- 
cotton  prepared  by  Mialhe's  process,  that  now  found  in  the  U.  S.  Pharma- 
copoeia. Last  winter  a  parcel  of  gun-cotton  was,  after  drying,  put  in  a 
wide-mouthed  vial  and  covered  with  paper  instead  of  a  cork.  On  recently 
examining  it,  the  cotton  had  undergone  a  complete  change,  the  odor  of 
nitrous  acid  was  quite  apparent  in  the  vial,  and  the  texture  of  the  paper 
cover  was  destroyed.  When  pressed  in  the  fingers  its  apparently  fibrous 
structure  was  lost,  and  a  gummy  mass,  exceedingly  adhesive,  remained, 
which  was  not  soluble  in  ether.  As  several  writers  have  noticed  the  same, 
or  analogous  changes,  and  some  light  has  been  thrown  on  its  cause  by  Mr. 
Gladestone,  we  will  make  a  few  statements  from  papers  in  the  Pharmaceuti- 
cal Journal. 
The  first  notice  is  by  Mr.  Tustin,  (vol.  IX.  405.)  He  had  prepared  gun- 
cotton  for  collodion,  by  Mialhe's  process,  and  put  it  away  in  a  corked  bottle 
for  several  months  in  a  dark  closet,  having  opened  it  from  time  to  time  to 
remove  portions, when,  on  the  last  occasion,  he  found  the  bottle  full  of  reddish- 
brown  vapours,  and  that  the  cotton  had  lost  its  explosibility,  had  a  strong 
acid  taste,  and  contained  evidences  of  nitric  and  sulphuric  acids,  though 
neutral  when  put  away.  Common  cotton  is  a  powerful  depolarizer,  whilst 
gun-cotton  does  not  depolarize  light.  Dr.  Pereira,  to  whom  this  gun-cotton 
was  shown,  writes: — "Your  decomposing  gun-cotton  agrees  with  common  cot- 
ton, though  its  depolarizing  properties  are  somewhat  weaker;  either,  there- 
fore, the  cotton  was  not  originally  properly  prepared,  or  it  has  resumed  its 
former  optical  characters,  and  simultaneously  has  given  out  an  oxide  of 
nitrogen  (either  N02    or  N04  )." 
Mr.  Tustin  here  leaves  the  inquiry,  after  stating  that  the  gun-cotton  was 
still  soluble  in  ether. 
Mr.  Jacob  Bell  (ibid.  40G)  had  known  a  similar  decomposition,  during 
which  a  tin  foil  cover  to  the  bottle  was  destroyed  by  the  acid  fumes. 
Mr.  J.  H.  Gladstone  has  examined  into  the  changes  which  gun-cotton 
and  analogous  substances  undergo,  more  critically  (ibid.  vol.  XI.  page  401,) 
and  we  extract  the  following  : 
"Gun-cotton,  as  ordinarily  produced,  especially  for  the  preparation  of  col- 
