ON  THE  PREPARATION  OF  GUN-COTTON. 
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ON  THE  PREPARATION  OF  COLLODION  WOOL  OR  GUN-COTTON 
By  C.  Mann. 
During  the  last  few  months  numerous  statements  have  been 
made  with  regard  to  the  preparation  of  collodion  wool,  from  the 
general  results  of  which  it  appears  that  in  adopting  the  several 
methods  certain  proportions  of  the  reagents  must  be  strictly  ad- 
hered to,  although,  frequently,  these  proportions  are  not  even  men- 
tioned in  the  directions  given. 
The  author  of  the  present  paper  has  made  a  series  of  experi- 
ments, with  a  view  to  determine  what  are  the  conditions  that  de- 
termine the  good  or  bad  quality  of  this  substance.  He  finds  that 
this  very  much  depends  upon  the  percentage  of  water  in  the  sul- 
phuric and  nitric  acids.  In  proportion  as  the  quantity  of  water  in 
the  mixture  exceeds  a  certain  normal,  either  the  collodion  wool  is 
bad  or  none  is  formed.  Very  concentrated  sulphuric  acid  yields  a 
product  which,  though  good  while  in  a  fresh  state,  decomposes  even 
at  the  ordinary  temperature;  more  dilute  acid,  on  the  contrary,, 
yields  a  worthless  product.  Neither  of  these  products  dissolve  in 
a  mixture  of  alcohol  and  ether.  According  to  the  state  of  hydra- 
tion of  the  acid,  the  cotton  may  be  obtained  of  different  characters, 
varying  gradually  from  an  extremely  soluble  form  to  one  which  is> 
equally  insoluble.  When,  by  the  use  of  too  concentrated  sulphu- 
ric acid,  an  insoluble  wool  has  been  obtained,  this  may  easily  be 
rendered  soluble  by  steeping  it  in  the  proper  mixture  of  acid,  and 
inversely  good  collodion  wool  may  be  rendered  insoluble.  Thus, 
for  instance,  cotton  treated  with  a  mixture  of  fourteen  parts  3 
(S03  HO)+HO,  and  twelve  parts  N05  HO,  yields  an  insoluble  pro- 
duct, which,  when  steeped  in  the  mixture  of  fourteen  parts  (HO)3 
S03  and  twelve  parts  N05  HO  is  converted  into  soluble  collodion 
wool.  As  a  general  rule,  the  conditions  which  determine  the  quali- 
ty of  the  product,  are,  1.  The  hydration  of  the  sulphuric  acid;  2. 
The  presence  of  a  certain  quantity  of  hyponitrous  acid  in  the  nitric 
acid  ;  3.  The  temperature  ;  and  4.  The  time  of  steeping. 
The  process  which  the  author  adopts  is  the  following: — Sulphu- 
ric acid  of  from  1.830  to  1.835  specific  gravity,  that  is,  of  ninety- 
four  per  cent,  of  monohydrate,  according  to  Ure  =  65°. 5  Baume, 
a1  59°. 9  F.,  and  represent!  by  the  f)rmula  3  (S03  HO)-f  HO  is 
mixed  with  nitrate  of  potash  and  cotton  wool,  neither  of  which 
require  to  be  dried,  in  the  following  proportions: — 
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