114         ON  COLLODION  AND  CANTHARIDAL  COLLODION. 
separated,  and  reduced  by  means  of  SO^.  The  reduction  may 
be  explained  by  the  following  equation  : 
2CrO^+3S02  =  Cr^O^+SSO^ 
The  sulphuric  acid  formed  combining  with  the  oxide  of  chromium 
to  one  equivalent  of  sulphate  of  chrome.    The  sulphate  of  chrome 
was  decomposed  by  ammonia ;  the  chromit  oxide  was  washed 
with  boiling  water  and  dried. 
This  preparation  has  been  used  with  great  success  in  this  city 
by  Dr.  Wilson  and  others,  in  the  treatment  of  cholera  infantum 
and  other  complaints  of  the  alimentary  canal. 
Dr.  F.  C.  Wilson,  of  New  York,  first  informed  me  of  its 
beneficial  effects  in  these  complaints,  and  at  his  suggestion  the 
preparation  was  made.  Its  mode  of  action  I  am  not  able  to  give, 
but  it  is  probably  that  of  an  astringent  and  tonic. 
Louisville,  Ky.^  Jan.  9,  1870. 
REMARKS  ON  COLLODION  AND  CANTHARIDAL  COLLO- 
DION. 
By  William  Silver  Thompson. 
The  unrecorded  experience  of  many  pharmacists  who  have 
prepared  collodion  and  collodion  cotton  has  probably  been  like 
my  own,  an  alternation  of  successes  and  failures;  and  without  at- 
tempting a  review  of  what  has  heretofore  been  written  on  the 
subject,  I  offer  the  following  remarks  and  formulas  ;  not  laying 
much  claim  to  originality,  except  in  some  points  considered  es- 
sential to  successful  results  in  conducting  the  processes  : 
For  preparing  collodion  cotton  I  prefer  a  mixture  of  nitric 
and  sulphuric  acids  of  the  officinal  sp.  gr.  to  the  sulphuric  acid 
and  nitrate  of  potassa  mixture  of  the  Pharmacopoeia  of  1860,  as 
being  less  troublesome,  less  expensive  and  affording  a  better  re- 
sult. The  most  important  point  to  be  observed  in  the  acid  mix- 
ture process  is  to  have  the  nitric  acid  of  the  officinal  sp.  gr.  The 
sp.  gr.  of  the  sulphuric  acid  is  not  of  so  much  importance ;  an 
acid  somewhat  stronger  than  the  officinal  may  be  used,  but  in  no 
case  of  a  less  sp.  gr.  When  the  acids  are  mixed  in  a  suitable 
glass  vessel  it  should  be  covered  with  a  plate  of  glass  and  placed 
in  a  vessel  of  cold  water  until  the  temperature  of  the  acid  mix- 
