ON  THE  PREPARATION  OF  GUN-COTTON. 
531 
D.        1  part  cotton  wool 
35  parts  3  (HO)9  S03  equiv.  =  174  spec.  grav.  1.780* 
33  parts  3  (SO,  HO)  4-  2  HO  equiv.  =  165 
17  parts  NaO  N06 
As  in  the  first  experiment  this  mixture  of  acid  and  salt,  after 
standing  for  twelve  hours  at  the  ordinary  temperature,  produced 
some  slight  blackening  and  solution  of  the  cotton-wool,  it  appeared 
probable  that  the  sulphuric  acid  had  not  had  sufficient  time  to  de- 
compose the  nitrate  of  soda  completely.  In  a  subsequent  experi- 
ment, therefore,  the  author  allowed  the  mixture  of  acid  and  salt  to 
stand  for  twenty-four  hours,  stirring  it  frequently.  On  then  intro- 
ducing the  cotton-wool  no  decoloration  took  place,  and  after  the 
mixture  had  stood  for  five  days  at  a  temperature  of  86°  F.,  the 
collodion  wool  obtained  proved  to  be  of  excellent  quality. 
From  the  definite  states  of  hydration  of  the  sulphuric  acid  requi- 
site for  the  nitrates  of  potash  and  soda  respectively,  it  may  be  seen 
what  must  be  the  state  of  the  sulphuric  acid  when  nitric  acid  is 
employed  instead  of  the  nitrates  in  the  preparation  of  collodion 
wool.  The  author  has  ascertained  by  experiment  that  among  the 
products  of  the  decomposition  of  KO  N05  +  3  S03  HO+  HO,  the 
member  KO  2  S03  is  of  no  importance  in  the  production  of  collo- 
dion wool,  and  that  this  is  likewise  the  case  among  the  products  of 
the  decomposition  of  NaO  N05  +3  S03  HO-f2HO,with  regard  to 
the  member  NaO  S03  +S03  HO.  Consequently  these  may  be  ex- 
cluded from  consideration,  and  then  the  mixtures  may  be  represented 
by  the  formulae 
S03  _+  N05  +  4  HO,  or  S03  3  H04-N05HO. 
which  is  the  appropriate  mixture  of  acids  for  preparing  collodion 
wool. 
E.    1  equiv.  S03  3  HO  spec.  grav.  =  1.632  =  56°  Baume 
1  equiv.  N05  HO  spec.  grav.=  1.518  to  1512  —  49.6  to 
49.12B. 
yield  a  mixture  which  converts  cotton-wool  into  excellent  collo- 
dion wool. 
When  the  sulphuric  acid  is  more  concentrated  and  the  nitric 
acid  more  dilute,  the  quantities  to  be  taken  of  each  so  as  to  have 
1  equiv,  S03  for  every  equiv.  N05  and  4  equiv.  HO,  may  be  de- 
termined by  calculation. 
For  preparing  collodion  wool  with  monohydrate  of  nitric  acid, 
the  quantities  to  be  taken  are : 
*  The  mixture  of  the  two  acids  had  a  specific  gravity  of  1.790=64°  B. 
