538 
ON  COLLODION. 
of  its  cheapness,  elegance,  and  safeness — will  prove  to  be  pre- 
ferable to  all  other  processes  hitherto  in  use.  The  same  process 
might  be  resorted  to  in  reducing  chloride  of  platina  and  the 
salts  of  copper. — Journ.  and  Trans.  Maryland  College  Pharm. 
Sept.  1758. 
ON  COLLODION. 
By  A.  P.  Sharp. 
As  this  article  has  become  quite  an  important  one,  not  only  to 
the  pharmaceutist  and  surgeon,  but  in  the  beautiful  art  of  Pho- 
tography— which  is  now  receiving  the  attention  of  many  scien- 
tific men  of  both  continents,  to  further  develope  the  mysterious 
power  of  that  imponderable  agent,  light — much  has  been  writ- 
ten and  many  formulae  given  for  its  preparation :  but  after  a 
careful  trial  of  a  great  portion  of  those  I  have  seen,  I  have  fal- 
len back  upon  the  one  I  have  successfully  used  for  several 
years,  and  now  propose  to  the  members  of  the  College,  at  the 
same  time  naming  its  advantage  over  most  of  the  other  plans 
recommended. 
It  will  be  remembered,  in  the  acid  process  a  very  strong 
nitric  acid  from  1.420  to  1.500  is  one  of  the  requisites  neces- 
sary to  obtain  a  good  article  of  cotton  soluble  in  ether.  The 
objection  I  have  to  this  mode,  is  the  great  difficulty  of  obtaining 
the  acid  of  the  proper  sp.  gr.,  as  the  commercial  article  seldom 
exceeds  1.400.  Again,  the  process  of  the  Pharmacopoeia,  where 
nitrate  of  potassa  is  the  agent  for  obtaining  the  three  atoms  of 
nitric  acid,  I  must  say  I  have  never  succeeded  satisfactorily  in 
obtaining  a  soluble  cotton,  there  always  being  a  considerable 
sediment  upon  standing  a  few  hours ;  and  further,  the  quantity 
of  sulphate  of  potassa  and  fumes  of  nitrous  acid  offer  a  serious  ob- 
jection to  my  mind ;  hence  I  have  endeavored  to  overcome  these 
difficulties,  which,  in  a  measure,  I  think  I  have  by  the  following 
process : — 
Take  of  Nitric  Acid,  1.40,  8  fluid  ounces, 
Sulphuric  Acid  (commercial),     -       16    "  « 
Nitrate  Potassa,  4  ounces, 
Finely  Carded  Cotton,      -  1  « 
