118  ON  THE  PRESERVATION  OF  FLUID  EXTRACTS. 
former,  but  made  with  a  different  and  more  spirituous  menstruum. 
But  a  more  striking  illustration  of  the  preservative  power  of  su- 
gar may  be  produced  by  the  following  experiment. 
Let  us  prepare  Liquor  Ferri  Iodidi  in  the  manner  prescribed  by 
the  Pharmacopoeia  ;  for  another  quantity  we  omit  the  sugar 
and  wash  the  filter  with  95  per  ct.  alcohol  instead  of  with  water, 
until  the  required  measure  is  obtained  ;  thus  we  procure  a  solu- 
tion of  iodide  of  iron  in  alcohol  of  72  per  ct.  of  the  strength  of 
the  liquor  of  the  Pharmacopoeia.  We  put  equal  measures  of  the 
two  solutions  in  two  vials  of  the  same  size  and  shape,  cover  their 
unstoppered  mouths  with  gauze  so  as  to  prevent  the  falling  in  of 
dust,  and  set  them  aside  in  a  place  where  the  direct  sunlight 
cannot  reach  them.  Thus  placed  in  as  nearly  as  possible  alike 
conditions,  the  progress  of  oxidation  may  be  easily  watched  and 
compared  without  disturbing  the  vials  and  mixing  the  different 
strata.  It  will  be  observed,  that  in  less  than  two  hours  the  lib- 
eration of  iodine  has  fairly  set  in,  in  the  alcoholic  solution,  while 
the  saccharine  liquid  apparently  shows  no  signs  of  decomposition 
yet ;  in  this  the  coloration  by  the  liberated  iodine  very  slowly 
proceeds  downwards,  the  former  has  in  12  hours  precipitated 
some  sesquioxide  of  iron  and  in  a  few  days  has  assumed  a  uni- 
formly deep  iodine  color. 
But  now  let  us  proceed  in  the  opposite  direction.  We  have  two 
similar  vials,  one  filled  with  a  saccharine,  the  other  with  an  alco- 
holic solution  of  iodide  of  iron  of  the  officinal  strength,  both  how- 
ever in  such  a  state  of  decomposition  that  the  shade  of  their  col- 
oration is  alike,  so  that  it  may  be  fairly  assumed  the  oxidation 
has  proceeded  equally  far  with  both  solutions.  Let  them  be  ex- 
posed to  the  direct  sunlight  under  similar  conditions,  and  in  such  a 
manner  that  both  may  be  easily  examined.  The  saccharine  so- 
lution, which  was  slowest  to  assume  the  coloration,  rapidly  ap- 
proaches to  colorlessness,  while  it  takes  a  much  longer  time  for 
the  spirituous  liquid. 
Both  these  experiments  tend  to  show  that  sugar  is  a  better  pre- 
servative and  a  better  deoxidizing  agent  than  alcohol ;  and  once 
come  to  this  conclusion,  we  must  acknowledge  it  as  desirable  to 
preserve  our  fluid  extracts  as  much  as  possible  by  means  of  su- 
gar. Our  aim  then  will  be  to  counteract  the  proneness  to  fer- 
mentation, which  in  many  cases  we  can  easily  achieve  by  the  ne- 
