292 
Extract  of  Malt. 
f  Am.  Jour.  Phariiw 
1      June,  1883. 
and  250  grams  water ;  a  good  thermometer  and  starch  mucilage  are 
needed  for  this  purpose. 
Ten  grams  starch  are  stirred  with  30  grams  of  water  and  poured  inta 
J  25  or  150  grams  of  boiling  water.  This  mixture  is  stirred  and  boiled 
for  some  time.  The  thermometer  is  then  introduced  and  the  mucilage 
is  allowed  to  cool  to  and  kept  at  a  temperature  of  100°  F.  by  means 
of  a  water-bath. 
Ten  grams  extract  of  malt  dissolved  in  10  cc.  water  are  then  stirred 
into  the  mucilage,  the  time  being  accurately  noted.  After  one  minute 
a  good  extract  will  have  converted  the  thick  mucilage  into  a  thin 
liquid.  As  soon  as  this  change  has  taken  place  it  is  necessary  ta 
examine  the  progress  of  the  conversion  of  starch  into  soluble  starchy 
dextrin  and  sugar  at  the  end  of  every  minute,  by  the  following 
method : 
After  the  expiration  of  the  first  minute  transfer  two  drops,  by  means- 
of  a  glass  rod,  into  one  of  the  2  oz.  bottles.  The  bottle  is  shaken  and 
placed  near  a  window.  At  the  end  of  every  minute  repeat  this 
manipulation  with  a  new  bottle  until  the  coloration  is  no  longer 
produced.  The  time  necessary  for  effecting  this  change  gives  the 
indication  as  to  the  amount  of  diastase  present.  Undecomposed  starch 
mucilage  gives  a  greenish  blue  color  and  after  standing  some  time  a 
blue  precipitate.  Soluble  starch,  the  first  product  of  the  change,  yields 
with  iodine,  a  dark  blue  solution  without  a  precipitate.  If  the  amount 
of  soluble  starch  equals  that  of  dextrin  and  sugar  the  color  of  the 
solution  will  be  purple.  As  the  soluble  starch  disappears  the  solu- 
tion will  be  of  a  decided  red  color  if  dextrin  predominates,  or  faintly 
red  if  the  sugar  be  in  excess ;  and  when  starch  and  most  of  the  dextrin 
have  been  converted  into  sugar,  the  liquid  will  be  nearly  or  entirely 
colorless.  This  experiment  is  very  interesting  and  is  simple  to  perform. 
A  good  extract  of  malt  should  convert  its  own  weight  of  starch 
within  ten  minutes  at  100°  F. ;  at  62°  F.  forty  minutes  will  be 
necessary  for  the  conversion,  and  at  150°  F.  only  three  minutes.  An 
extract  of  malt  of  the  above  strength  will  convert  five  times  its  weight 
of  starch  at  100°  F.  in  forty  minutes  and  eight  times  that  amount  in 
ninety  minutes. 
Furthermore,  an  extract  of  malt  which  converts  its  own  weight  of 
starch  at  100°  F.  in  ten  minutes  into  dextrin  and  sugar  will  in  the 
following  tin^.e  digest  the  following  boiled  amylaceous  articles  : 
