532  ON  THE  PREPARATION  OF  GUN-COTTON. 
F  1  part  cotton  wool 
13  parts  S03  3  HO  equiv.=67 
12  parts  N05  HO  equiv.  =  63 
Further,  when  from  the  mixture  of  nitrate  of  potash  ami  sulphu- 
ric acid  =  KO  N05  +  2  (3  S03  HO +  2  HO)  the  KO  2  S03  is, 
as  above,  disregarded,  a  second  prescription  for  the  preparation  of 
collodion  wool  is  obtained.    There  then  remain 
4  S03  +  N05  +  10  HO,  or  3  (S03  2  HO)  +  S03  3  HO  +  N05 
HO.    The  same  result  is  obtained  when 
NaO  S03  +  S03  HO  is  deducted  from  NaO  N05  +2  (3  S03  HO)  +  2 
HO  +  HO.  According  to  the  formula  then  deduced  the  following 
quantities  must  be  taken  : 
G  1  part  cotton  wool. 
33  parts  3  S03  2  HO 
13  parts  S03  3  HO 
12  parts  N05  HO 
The  mixture  of  the  two  acids  has  a  sp.  gr.  of  1.753  or  1.750  = 
63°  B. 
Collodion  wool  may  be  prepared  both  with  the  nitrates  of  potash 
or  soda,  and  in  a  much  shorter  time  than  has  been  stated  above, 
when  the  cotton-wool  is  treated  with  them  for  about  an  hour,  at  a 
temperature  of  104°  or  122^  F.,  and  this  is  likewise  the  case  with 
a  mixture  of  nitric  acid  and  the  double  quantity  of  sulphuric  acid. 
But  the  mixture  of  thirteen  or  fourteen  parts  S03  3  HO  and  12 
NO^  HO  does  not,  when  the  latter  acid  is  very  yellow,  bear  so 
high  a  temperature,  and  not  even  the  ordinary  temperature,  because 
the  hyponitrous  acid  generated  alters  the  character  of  the  collodion 
wool,  at  least  in  so  far  that  its  solution  in  a  mixture  of  alcohol 
and  ether  gives,  when  evaporated  upon  a  glass  plate,  an  opales- 
cent layer,  and  not  a  transparent  one,  like  good  collodion  wool- 
When  the  monohydrate  of  nitric  acid  contains  much  hyponitrous 
acid,  the  layer  has  a  milky  appearance,  and  inversely  the  collodion 
layer  is  clearer  and  more  colorless  the  smaller  the  quantity  of  hy- 
ponitrous acid  present  in  the  liquid  with  which  it  is  prepared. 
When  cotton  wool  is  treated  with  the  mixture  of  sulphuric  and 
nitric  acids,  at  the  temperature  of  32°  F.,  collodion  wool  is  formed, 
but  very  slowly  and  imperfectly.  The  temperature  of  41°  or  46.5° 
F.,  appears  to  be  the  most  favorable. 
Collodion  wool  prepared  according  to  any  one  of  the  methods 
