ON  THE  PRESERVATION  OF  FLUID  EXTRACTS.  219 
The  laws  which  govern  vinous  and  acetous  fermentation  are 
entirely  different.  The  former  is  easily  excited  and  rapid  in 
its  operation ;  the  latter  is  hard  to  excite  and  slow  in  its  opera- 
tion ;  the  former  proceeds  without  the  aid  of  oxygen;  the  latter 
consumes  large  quantities  of  oxygen.  Vinous  fermentation  is 
easily  induced  in  closed  vessels,  acetous  fermentation  requires 
free  and  continued  exposure  to  the  air,  and  a  ferment  differing 
in  nature  from  that  required  for  the  former.  Acetous  fermen- 
tation occurs  in  syrups  and  saccharine  fluid  extracts,  but  here  it 
must  be  preceded  by  the  vinous.  I  think  then,  that  the  natu- 
ral change  of  sugar  which  takes  place  without  oxygen  is  more 
to  be  feared  than  the  natural  change  of  alcohol  which  requires 
oxygen. 
The  writer  differs  from  my  opinion  that  saccharine  fluid  ex- 
tracts are  more  liable  to  undergo  fermentation  than  officinal 
syrups,  because  « the  nearer  the  density  of  organic  matter  ap- 
proaches solidity  and  dryness,  the  less  is  its  proneness  to  under- 
go such  a  change."  Unfortunately,  the  directions  for  using 
sugar  in  fluid  extracts  do  not  point  to  any  nearer  approach  to 
solidity.  From  twelve  to  fourteen  ounces  troy  of  sugar,  and 
the  contained  vegetable  matter,  form  a  fluid  extract  that  "  will 
generally  be  nearly  of  the  density  of  our  ordinary  syrups,"  the 
theory  being,  I  suppose,  to  approach  as  nearly  as  possible  to  the 
specific  gravity  1.319  in  both  preparations.  In  syrups  there  is 
more  sugar  and  less  vegetable  matter  ;  in  saccharine  fluid  ex- 
tracts there  is  less  sugar  and  more  vegetable  matter. 
But  there  are  changes  other  than  acetous  fermentation  pro- 
duced by  oxygen  in  vegetable  matter.  This  is  illustrated  by 
the  deposits  which  occur  in  officinal  tinctures.  These  deposits, 
it  is  argued,  are  due  to  the  natural  absorption  of  oxygen  by  al- 
cohol. Not  entirely.  They  are  owing  in  as  great  a  degree  to 
the  natural  evaporation  of  the  alcohol,  which,  lowering  the  per- 
centage of  the  menstruum,  and  in  consequence  its  power  of  solu- 
tion, allows  a  part  of  the  contained  matter  to  fall.  The  article 
allows  that  greater  changes  would  take  place  if  water  was  sub- 
stituted for  alcohol ;  so  would  greater  changes  take  place  if  for 
alcohol  solution  of  sugar  was  substituted.  "  The  decomposi- 
tion would  have  been  in  another  direction,"  a  quicker  and  more 
fatal  one.    The  real  advantage  in  using  alcohol  as  a  menstruum, 
