ON  PYROXYLIN. 
221 
without  being  supported  by  the  amount  of  the  yield.  In  fact, 
the  new  formula  supposes  a  yield  of  177*78  of  pyroxylin  for 
100  of  cotton,  while  the  old  formula  corresponds  to  a  yield  of 
only  175.  The  direct  experiments  described  above  gave  the  fig- 
ure 178. 
All  the  gun-cottons  we  analysed  were  previously  washed  in  a 
mixture  of  alcohol  and  ether,  to  remove  some  milliemes  of  fatty 
and  soluble  matters,  then  dried  for  several  hours  in  a  stove  at 
a  temperature  between  40  and  50°. 
All  were  of  the  composition  above  described^  and  gave  the 
following  figures : — 
Carbon  25-00 
Hydrogen    ......  3-13 
Oxygen  59-72 
Nitrogen     ......  12-15 
100-00 
The  Action  of  Heat  on  Pyroxylin, — General  Lenk  ascribes 
the  unsatisfactory  results  obtained  in  France  by  the  Commission 
of  1846  to  the  fact  that  not  sufficient  attention  was  paid  to  the 
manner  in  which  the  pyroxylin  was  prepared,  and  to  operating 
upon  an  insufficiently  defined  nitred  product.  By  taking  ad- 
vantage of  conditions  most  favorable  to  nitrogenisation,  he  be- 
lieves he  has  obtained  a  pyroxylin  very  difficult  to  decompose. 
We  will  not  discuss  the  theoretical  value  of  this  assertion, 
which  does  not  seem  to  us  to  be  very  great.  It  is,  on  the  con- 
trary, more  probable  that  gun-cotton  would  decompose  more 
readily  the  less  like  cellulose,  and,  consequently,  the  more  ni- 
tred it  became.  However  this  may  be,  General  Lenk  says  that 
pyroxylin  made  by  his  process  will  not  explode  below  136°  C. 
We  have  made  this  important  point  the  subject  of  numerous 
experiments. 
These  experiments  were  first  made  with  an  experimental 
matrass,  open  or  closed,  and  plunged  into  a  bath  of  boiling 
water. 
All  the  samples  heated  in  this  way  to  100°  were  sooner  or 
later  decomposed,  and  in  a  few  minutes  a  disengagement  of  ni- 
trous vapors  took  place. 
The  decomposition  takes  place  in  different  ways,  and  can- 
