530 
ON  THE  PREPARATION  OF  GUN-COTTON. 
A         1  part  cotton  wool 
31  parts  3  (S03  UOJ  +  HO  equiv.=  156 
20  parts  KO  NO,  equiv.=  101 
The  powdered  nitrate  is  mixed  wiih  the  sulphuric  acid  in  a  glass 
cylinder,  the  mixture  stirred  until  the  nitrate  is  entirely  dissolved. 
Into  this  mixture  while  still  warm,  but  not  at  all  more  than  122° 
Fah.,  the  cotton  wool  is  introduced  and  agitated  with  a  rod  until 
perfectly  saturated  with  the  acid  liquid.  The  cylinder  is  then  to 
be  covered  with  a  glass  plate,  and  the  whole  left  to  stand  for  about 
twenty-four  hours  at  a  temperature  of  84.4°  or  86°  F.  The  mix- 
ture is  then  placed  in  a  porcelain  mortar,  and  washed  with  cold 
water,  until  the  wool  has  no  longer  an  acid  reaction.  The  moist 
wool  is  finally  freed,  by  treatment  with  boiling  water  from  the  last 
traces  of  sulphate  of  potash,  which  is  very  obstinately  retained  by 
the  cotton  fibres,  and  communicates  to  the  collodion  solution  an 
opalescent  appearance. 
When  the  cotton  wool  is  allowed  to  remain  for  five  or  six  days 
in  the  mixture  at  a  temperature  of  86°  F.  the  collodion  wool  is 
improved  in  quality.  When  the  steeping  is  continued  only  for 
ten  or  twenty  minutes,  the  product  is  less  perfect. 
Collodion  wool  may  likewise  be  obtained  with  nitrate  of  soda, 
in  which  case,  however,  sulphuric  acid  of  1.800  sp.  gr.=  64c.5 
J3aume  is  requisite.    This  acid  may  be  represented  by  the  formula 
3  (S03  HO) +  2  HO.    The  proportion  to  be  used  are  :— 
B.  J  part  cotton  wool 
33  parts  3  (S03  HO)  +  2  HO  equiv.=  165 
17  parts  NaO  NO.-  equiv.=  85 
Other  mixtures  of  sulphuric  acid  and  nitrate  of  potash  or  soda 
may  be  made,  which  yield  equally  good  or  even  better  collodion 
wool  when  applied  to  the  cotton  in  different  proportions.  Thus 
the  author  made  experiments  with  the  following  mixtures: 
C.       2  parts  cotton  wool 
66  parts  2  [3(S03  HO)+2HO]  equiv.  330 
20  parts  KO  N05 
The  sulphuric  acid  which  is  used  with  nitrate  of  soda,  and  in 
which  case  a  double  quantity  is  requisite,  must  possess  a  different 
composition,  namely: — 
2  [3  (S03  HO)  +  2HOJ+HO  =  3  (HO),  S03+  3  S03  HO+2  HO. 
Further,  collodion  wool  is  obtained  by  using  : 
