408 
Ferric  Chlorides. 
/Am.  Jour.  Pharm. 
\     August,  1884. 
the  inference  is  fair  that  this  excess  is  needed  to  prevent  decomposition 
during  the  application  of  heat.  But  a  portion  of  it  is  intentionally 
added  for  the  presumptive  generation  of  an  ether  when  the  liquor  is 
compounded  into  tincture.  As,  however,  this  ether  is  considered  an 
essential  component  of  the  tincture  in  whose  production  three  months 
of  time  are  given,  it  follows,  that  be  the  creative  agent  what  it  may,  it 
cannot  be  officially  viewed  as  an  undesirable  contamination.  Now,  the 
Pharmacopoeia  has  been  very  solicitous  to  employ  only  nitric  acid  in 
the  development  of  ferric  salts  in  general  and  to  expel  any  excess  by 
means  of  heat.  It  can  be  easily  shown  that  it  is  impossible  to  get  rid 
of  the  nitric  acid  in  this  manner.  The  expulsion  of  the  lower  oxides 
of  nitrogen  is  not  even  attainable  by  this  method.  It  can  be  further 
shown  that  the  production  of  the  ether  depends  upon  the  presence  of 
these  oxides  of  nitrogen  exclusively  and  that  the  chlorhydric  acid  has 
no  share  in  the  performance.  To  remove  all  doubt  in  this  connection, 
the  writer  made  three  mixtures,  preserved  in  well-stopped  bottles,  the 
first  being  composed  of  one  part  of  chlorhydric  acid  and  nine  parts  of 
alcohol ;  the  second  of  one  part  of  chlorhydric  acid  and  four  parts  each 
of  water  and  alcohol,  and  the  third  of  one  part  of  nitric  acid  and  four 
parts  each  of  water  and  alcohol.  After  months  of  standing  the  first 
two  mixtures  possessed  no  odor  but  that  of  alcohol.  After  several 
days'  standing  the  third  mixture  had  developed  the  unmistakable  odor 
of  ethyl  nitrite  and  at  the  same  time  began  to  effervesce  slightly,  espe- 
cially on  shaking.  The  effervescence  finally  ceased,  but  the  fragrance 
in  the  meantime  had  become  much  stronger.  When  solution  of  ferric 
chloride  containing  some  nitric  acid  is  mixed  with  alcohol,  or  either 
alcohol  and  water,  a  very  dark,  sometimes  nearly  black  color  is  soon' 
produced,  and  shortly  after  nitrogen  tetroxide  is  copiously  evolved. 
Eventually  the  fuming  ceases  and  the  color  assumes  a  much  lighter 
shade.  However,  the  tint  permanently  remains  many  shades  deeper 
than  that  of  a  similar  combination  free  from  nitric  admixture.  The 
colored  product,  after  the  main  reaction  is  over,  is  always  characterized 
by  the  odor  of  ethyl  nitrite.  If  the  very  dark  solution  at  the  incipi- 
ency  of  the  reaction  is  subjected  to  heat,  a  violent  effusion  of  nitrogen 
tetroxide  results,  and  the  deep  hue  is  simultaneously  discharged,  leav- 
ing only  the  normal  color  of  ferric  chloride.  Incidentally  during  this 
operation  the  odor  of  nitrous  ether  also  disappears  and  is  not  regener- 
ated during  any  subsequent  period  of  storage.  It  is  well  known  that 
when  MonseFs  solution  is  evaporated  a  pasty,  deliquescent  residue 
