136  Diastasic  Power  of  Extract  of  Malt.  {^mS.S01* 
manufacture,  as  might  be  suggested  by  the  low  results  of  the  Eng- 
lish experimenters;  on  the  contrary,  from  the  experience  of  large 
numbers  of  determinations,  I  am  strongly  of  opinion  that  (gener- 
ally speaking)  English  extracts  are  distinctly  superior  to  either 
American  or  German  ones. 
In  the  first  place  I  will  describe  the  method  I  am  in  the  habit  of 
using,  for  which  I  do  not  claim  any  originality,  it  being  simply  a 
modification  of  the  foregoing  processes: 
(1)  Prepare  a  mucilage  by  mixing  1  grm.  of  potato  starch  or 
arrow-root  (dried  in  an  oven  at  21 2°  F.)  with  10  cc.  of  cold  water, 
add  100  cc.  of  boiling  water,  and  boil  the  whole  for  half  an  hour; 
allow  to  cool  to  about  ioo°  F.,  and  make  up  the  measure  to  100  cc. 
(2)  Dissolve  5  grms.  of  the  sample  of  extract  of  malt  in  water 
sufficient  to  produce  50  cc.  of  solution. 
(3)  Dissolve  -i  grm.  iodine  in  100  cc.  of  water  by  the  aid  of  -2 
grm.  of  iodide  of  potassium. 
50  cc.  of  starch  solution  is  introduced  into  a  flask  or  bottle  and 
kept  in  a  water-bath  at  a  temperature  of  9S0  to  ioo°  F.  until  it  has 
attained  that  temperature,  when  5  cc.  of  the  malt  solution  is  added 
(also  at  98°-ioo°  F.)  gently  shaken  to  mix:  thoroughly,  and  replaced 
in  the  water-bath ;  after  five  minutes  and  at  intervals  of  five  minutes 
(or  less  if  found  desirable)  4  cc.  of  the  liquid  is  poured  into  a  test- 
tube  containing  1  cc.  of  the  iodine  solution.  A  good  extract  of 
malt  will  give  no  indication  of  starch  or  dextrin  after  ten,  or  at 
most,  fifteen  minutes,  while  one  which  still  gives  a  distinct  colora- 
tion after  thir'iy  minutes  should  be  rejected  as  quite  unfit  for  use; 
0-5  grm. 
o-i  grm. 
0-05  grm. 
5  min. 
15  min. 
50  min. 
45  min. 
5  min. 
15  min. 
30  min. 
5  min. 
10  min. 
15  mm. 
30  min . 
Ar.rowroot, 
Done 
Done 
Bhtbrn 
Pale 
Done* 
brown 
Maize,   .  . 
Bluish 
Bluish 
Done 
Indigo 
Indigo 
Violet 
Clear 
blue 
bluet 
Potato,  .  . 
Done 
Done 
Bht  brn 
Pale 
Donef 
brown 
Rice,  .  .  . 
Bluish 
Pale  bl. 
Done 
Blue 
Bluish 
Pale  vlt 
Clear 
brown 
violet 
Wheat,  .  . 
Brown- 
Violet 
Violet 
Very 
Brown- 
Violet 
Purple 
Clear 
ish 
brown 
tint 
pale 
violet 
violetf 
Violet 
violet 
*  Completed  in  twelve  minutes. 
|  Completed  in  twelve  and  a  half  minutes. 
i  These  colors  refer  to  the  liquid  five  times  diluted  ;  the  color  was  too  deep 
to  be  seen  before  dilution. 
