PROPER  MENSTRUUM  FOR  FLUID  EXTRACTS.  307 
fruits  are  capable  to  undergo  vinous  fermentation  in  an  atmos- 
phere of  carbonic  acid,  and  according  to  Doepping  and  Struve, 
grapes  will  ferment  likewise  in  an  atmosphere  of  hydrogen,  with- 
out forming  any  yeast-cells.  All  these  experiments  have  been 
made  with  fruits,  which  in  their  cells  include,  besides  sugar  and 
water,  vegetable  acids  and  bodies  related  to  pectin.  Now  the 
transmutation  of  pectose  by  pectase  into  pectin  and  similar  allied 
compounds,  and  the  influence  of  vegetable  cells  which  most 
likely  have  not  been  all  torn  by  the  expression  which  was  per- 
formed in  a  space  excluded  from  the  air,  are  potent  agents  for 
the  decomposition  of  organic  matter,  and  probably  of  the  utmost 
importance  for  this  phenomenon.  This  sort  of  fermentation  has 
no  bearing  on  the  case  of  our  fluid  extracts.  Let  us  see  what 
Liebig  observes  in  regard  to  exciting  fermentation  in  solutions. 
In  his  "  Agricultural  Chemistry,"  translated  by  Dr.  Playfair, 
Philadelphia  edition,  page  96,  he  states  that  "  neither  the  soluble 
nor  the  insoluble  part  of  ferment  causes  fermentation,"  and  then 
continues  :  "Before  it  (the  soluble  part)  obtains  this  power,  the 
decanted  infusion  must  be  allowed  to  cool  in  contact  with  the 
air,  and  to  remain  some  time  exposed  to  its  action.  .  .  .  Yeast 
produces  fermentation  in  consequence  of  the  progressive  decom- 
position which  it  suffers  from  the  action  of  air  and  water." 
And  in  another  place  it  is  stated,  that  "  its  action  is  arrested  by 
the  temperature  of  boiling  water,  by  alcohol,  common  salt,  an 
excess  of  sugar,  oxide  of  mercury,  corrosive  sublimate,  pyrolig- 
neous  acid,  sulphurous  acid,  nitrate  of  silver,  volatile  oils  and  in 
short  by  all  antiseptic  substances." 
Having  on  page  119  of  this  Journal  spoken  of  the  density  of 
saccharine  fluid  extracts,  the  subsequent  remarks  appear  to 
have  been  misunderstood.  The  idea  intended  to  be  conveyed,  is 
that  the  liability  of  saccharine  liquids  to  fermentation  is  not  in- 
creased in  the  proportion  of  the  increase  of  ferment,  inasmuch 
as  a  small  quantity  of  ferment  is  able  to  convert  a  large  amount 
of  sugar  into  alcohol,  (1-5  parts  dry  yeast  to  100  parts  crystal- 
lized sugar,  Thenard;)  this  liability  is  in  a  higher  degree  de- 
pendent on  the  density  of  the  solution,  and  the  higher  we  make 
the  specific  gravity  of  our  fluid  extracts,  the  nearer  they  ap- 
proach to  solidity,  the  less  will  be  their  proneness  to  fermenta- 
tion. 
