218 
ON  FORMIC  ACID. 
Iodo- Sulphur al  Collodion. 
Take  of  Iodine,      ....      half  an  ounce. 
Sulphur,    ....       a  drachm. 
Balsam  of  Fir,  .       .       .       half  an  ounce. 
Collodion,  ....       a  pint. 
Mix. 
These  furnish  an  elegant  method  of  exhibiting  sulphur  and 
iodine,  far  more  cleanly  than  when  mixed  in  ointment,  and  with- 
out the  intensely  disagreeable  smell  of  that  preparation  ;  while 
in  many  cases  of  skin  diseases  there  is  an  advantage  in  the 
coating  of  cotton.  It  is  unnecessary  to  use  iodide  of  sulphur, 
as  the  collodion  decomposes  it,  dissolving  the  iodine  while  the 
sulphur  is  precipitated.  Of  course  the  bottles  must  be  well 
shaken  before  applying  the  liquid. 
Formulas  for  other  similar  preparations  may  occur  to  the 
apothecary,  the  foregoing  being  given  to  call  attention  to  the 
method.  The  collodions  should  be  dispensed  in  small  vials  with 
a  camel's  hair  pencil  inserted  in  the  cork. 
Philadelphia,  4:th  month,  1858. 
ON  FORMIC  ACID. 
By  Edwakd  Fell. 
(An  Inaugural  Essay  presented  to  the  Philadelphia  College  of  Pharmacy,  1858.) 
Having  had  occasion  lately  to  make  some  formic  acid  to  sup- 
ply an  order,  and  becoming  interested  in  the  results,  I  concluded 
to  make  it  the  subject  of  my  thesis. 
When  wood  is  subjected  to  destructive  distillation,  there  is 
obtained,  in  addition  to  other  products,  a  volatile  inflammable 
liquid,  mixed  with  acetone,  aldehyd,  and  other  substances,  called 
pyroxylic  spirit,  (impure  methylic  alcohol,)  which  can  be  purified ' 
by  successive  distillations  with  lime. 
Having  some  impure  pyroxylic  spirit  at  my  disposal,  I  proceeded 
to  make  some  pure  methylic  alcohol.  The  formula  used  was  that 
given  in  the  American  Journal  of  Pharmacy,  vol.  xxv.  Half  a 
pound  of  the  impure  spirit  was  mixed,  very  gradually,  to  prevent 
over-heating,  with  half  a  pound  of  strong  sulphuric  acid.  When 
cool,  one  pound  of  binoxalate  of  potassa  was  added  to  the  mix- 
