16 
Analysis  of  Halt  Extract. 
( Am.  Jour.  Pharm. 
t      Jan.,  1885. 
which  the  clialisator  was  placed  renewing  itself  constantly.  After  24 
hours  the  solution  in  the  dialisator  still  had  a  fresh  odor,  showed  little 
acid,  and  scarcely  gave  with  a  solution  of  iodine  a  red  color,  while  the 
solution  in  the  bottle  had  assumed  a  very  unpleasant  smell,  tasted  very 
sour,  and  still  contained  a  large  amount  of  undecomposed  starch, 
which,  on  an  addition  of  2  parts,  by  weight,  of  extract,  did  not  dis- 
solve. 
Two  extracts  of  equal  amounts  of  diastase  may  contain  unequal 
amounts  of  acids,  and  then  act  differently  on  starch,  as  has  been  proven 
by  the  tables  given  in  my  previous  paper.  For  this  reason  the  amount 
of  acid  should  always  be  determined  before  examining  the  diastatic 
effect,  and  should,  in  a  carefully  prepared  extract,  and  calculated  as 
lactic  acid,  never  exceed  1*085  per  cent,  for  every  100  parts  of  dry 
substance. 
If  the  amount  of  acid  is  larger,  the  acid  should  first  be  neutralized, 
and  following  this  the  effect  of  the  diastase  should  be  examined. 
A  neutralized  malt  extract  will  certainly  not  act  as  rapidly  on  starch 
as  an  acid  extract  will.  For  instance,  a  malt  which  is  not  ueutralized 
will  act  on  an  equal  weight  of  starch  in  2  and  5  minutes,  respectively, 
at  100°F. ;  after  the  acid  is  neutralized  it  will  dissolve  the  same 
amount  of  starch  in  the  same  time,  but  at  a  temperature  of  150°F. 
Considering  that  commercial  starch  is  not  always  of  the  same  qua- 
lity, more  precise  examinations  require  for  use  a  filtered  solution  of 
starch  paste,  in  which  the  amount  of  starch  has  been  determined. 
After  uniiltered  starch  has  been  wholly  transformed  into  gum  and 
dextrin,  its  membranes  are  attacked  and  require  a  long  time  for  dis- 
solving. Therefore  it  often  occurs  that  after  iodine  shows  no  coloring 
a  violet  color  may  again  be  produced  after  the  lapse  of  a  few  minutes. 
These  reactions  will  pass  off  smoothly  by  using  the  filtered  starch 
solution. 
For  neutralizing  the  acid  I  mix  well-washed  and  still  moist  carbon- 
ate of  magnesium  with  a  10  })er  cent,  solution  of  malt  extract,  shake 
until  the  acid  reaction  has  disappeared,  filter,  and  add  the  requisite 
quantity  of  starch  paste.  This  method  should  always  be  resorted  to 
as  a  check  experiment  for  the  determination  of  diastase.  For  ascer- 
taining the  effect  of  diastase  on  large  quantities  of  starch  we  should 
always  use  the  dialisator. 
Remarks  on  the  Testing  with  Iodine. — Respecting  the  addition  of  the 
solution  of  iotline  to  the  water,  with  which  the  reaction  upon  starch  is 
