Off  THE  PRESERVATION  OF  FLUID  EXTRACTS.  119 
cessarj  quantity  of  sugar  which  of  itself  protects  sufficiently  the 
vegetable  matter  against  oxidation  in  general,  that  cannot  be 
avoided  by  the  use  of  alcohol,  this  antiseptic  itself  having  a  ten- 
dency to  undergo  acetic  fermentation  through  the  influence  of 
sundry  vegetable  substances.  One  great  objection,  and  I  think, 
a  more  serious  one  than  fermentability,  is  the  different  degree  of 
solubility  of  sugar  in  water  at  a  temperature  of  such  variation  as 
is  experienced  in  our  climate  during  the  summer  and  winter  sea- 
son when  it  verges  almost  on  impossibility  to  maintain  constant- 
ly in  a  given  space  a  temperature  of  about  60°F.,  which  has  been 
found  most  salutary  for  syrups.  Fluid  extracts,  of  course,  ought 
to  be  made  to  withstand  these  changes  as  far  as  they  are  felt  in- 
side the  house,  in  the  cellar,  and  in  the  dispensing  room.  A 
saccharine  fluid  extract,  containing  in  a  pint  12,  never  over  14 
ounces  Troy  of  the  best  sugar,  is  not  apt  to  crystallize  in  moder- 
ately cold  weather,  and  as  it  is  charged  with  a  considerable 
amount  of  vegetable  matter,  it  will  then  generally  be  nearly  of 
the  density  of  our  ordinary  syrups  containing  15  oz.  Troy  of  su- 
gar in  one  pint.  The  exact  quantity  of  sugar  necessary  for  preser- 
vation, and  particularly  to  resist  fermentation,  varies  in  different 
cases,  those  plants  yielding  a  large  amount  of  soluble  matter  re- 
quiring less  sugar  than  those  yielding  but  little.  I  differ  from  M. 
Thayer's  opinion,  that  because  containing  more  vegetable  matter 
— natural  ferment  as  he  calls  it — saccharine  fluid  extracts  are 
more  liable  to  undergo  change,  fermentation  ;  on  the  contrary, 
the  nearer  the  density  of  organic  matter  approaches  solidity  and 
dryness,  the  less  is  its  proneness  to  such  a  change,  and  infusions 
of  a  marked  difference  in  their  strength,  made  alike  and  placed 
under  the  same  influences,  will  show  the  weaker  to  change  before 
the  stronger,  but  more  especially  will  this  be  the  case  when  the 
weaker  infusion  has  been  concentrated  by  evaporation  and  fil- 
tered. 
Thus  far  I  have  spoken  of  the  preference  of  sugar  over  alco- 
iiol  from  a  chemical  point  of  view,  and  the  question  remains  now 
to  be  reviewed  in  a  pharmaceutical  light,  concerning  appearance 
and  taste. 
With  some  well  known  exceptions,  a  liquid  medicine  is  the 
m  ore  pleasing  to  the  eye,  the  more  transparent  and  clear  it  is. 
Those  rendered  turbid  by  some  partially  soluble  substance,  are 
