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ON  THE  PREPARATION  OE  COLLODION. 
ON  THE  PREPARATION  OF  COLLODION. 
By  Oliver  G.  Sherman. 
(An  Inaugural  Essay  presented  to  the  Philadelphia  College  of  Pharmacy,  1858.) 
Although  collodion  is  extensively  used  in  the  arts,  and,  to  a 
more  limited  extent,  in  surgery,  yet  the  chemical  changes  and 
causes  of  disappointment  in  its  preparation  are  little  under- 
stood ;  thereby  rendering  its  manufacture  one  of  much  trouble 
and  perplexity,  and  oftentimes  resulting  in  entire  failures.  I  do 
not  design  to  enter  fully  into  the  rationale  of  the  minute  chemi- 
cal changes  which  take  place,  but  simply  to  notice  some  of  the 
causes  .which  most  frequently  give  rise  to  disappointment,  and 
to  give  a  practical  formula,  so  that  pharmaceutists  may  meet 
with  success  when  they  undertake  its  preparation.  This  formula 
I  shall  endeavor  to  construct  in  accordance  with  a  few  rules, 
which  have  been  found  necessary  to  follow. 
To  the  kindness  of  my  friend,  Mr.  Benj.  J.  Crew,  I  am  in- 
debted for  much  of  my  knowledge  of  this  preparation,  and  with 
his  approbation  have  instituted  this  article.  During  my  experi- 
ments to  obtain  a  soluble  cotton,  I  have  taken  particular  notice 
of  the  different  textures  and  solubilities  which  resulted,  and 
have  found  that  they  were  modified  according  to  the  strength 
and  temperature  of  the  nitro-sulphuric  acid  used.  The  formula 
of  the  U.  S.  Pharmacopoeia,  directs  the  use  of  nitrate  of  potassa  ; 
this  process  is  constantly  causing  unsatisfactory  results,  and,  at 
the  present  time,  is  almost  entirely  abandoned,  when  made  in 
large  quantities,  for  that  of  the  two  acids.  My  experiments  were 
made  with  the  latter,  and  I  shall,  therefore,  confine  my  remarks 
accordingly,  Much  depends  on  the  strength  of  these  acids. 
The  temperature  of  those  of  a  proper  strength,  when  mixed, 
should  rise  from  70g  F.  to  about  135°  F.;  this  temperature  being 
necessary  to  effect  a  soluble  cotton.  But  the  temperature  alone, 
to  which  they  rise,  is  no  criterion  for  success,  unless  their  specific 
gravities  and  temperatures  were  previously  noticed.  When  cot- 
ton is  added  to  nitro-sulphuric  acid,  the  following  is  thought,  by 
some  authorities,  to  be  the  chemical  change :  The  nitric  acid 
undergoes  decomposition ;  while  the  cotton,  a  change  of  substi- 
tution. One  equivalent  of  nitric  acid  is  decomposed  into  one 
equivalent  of  peroxide  of  nitrogen  (N04),  and  one  of  oxygen  ; 
