142  Method  of  Testing  Diastatic  Substances.  {  *mM£ch,im™' 
posed  test  method  is  based  upon  the  stable  diastatic  property  of 
Taka-Diastase. 
So  far  as  is  generally  known,  and  it  is  also  my  own  experience, 
that  the  diastase  isolated  from  malt,  and  that  precipitated  principle 
of  saliva  known  as  ptyaline,  lose  their  diastatic  power  by  standing. 
Therefore,  when  the  diastatic  power  of  any  substance  is  to  be  deter- 
mined, it  is  necessary,  if  they  are  used,  to  go  through  the  long  pro- 
cess each  time  of  determining  the  quantity  of  sugars  formed  by 
their  action  on  starch(Lintner's  method),  or  else  measure  the  length 
of  time  required  to  convert  the  given  quantity  of  starch  into  sugar 
(Junk's  method).  While  these  processes  have  valuable  merits  of 
their  own,  yet  they  have  the  disadvantage  of  being  rather  compli- 
cated for  quick,  everyday  work.  In  carrying  out  my  proposed 
method,  a  quantity  of  Taka-Diastase  is  tested  by  either  of  the  above- 
mentioned  processes  (Lintner's  or  Junk's1),  and  its  exact  diastatic 
power  determined  once  for  all.  The  diastatic  power  may  be  expressed 
as,  say,  300  Lintner's  units,  or  it  may  be  expressed  as  converting 
100  times  its  own  weight  of  dry  starch  into  sugar  in  ten  minutes. 
The  diastatic  power  of  any  substance  under  examination  is  now 
compared  with  the  standardized  sample,  and  expressed  in  any  terms 
desired,  either  directly  or  by  simple  calculation.  It  is  highly  de- 
sirable that  one  standard  should  be  adopted,  and,  whatever  that  may 
be,  the  following  comparative  test  will  be  found  useful.  First  pre- 
pare the  following  solutions  : 
(/)  Standard  Taka-Diastase  Solution. — Dissolve  1  gramme  of 
standarized  Taka-Diastase  solution  in  100  c.c.  of  water;  this  so- 
lution ought  to  be  made  fresh  each  day. 
(2)  Starch  Solution. — Make  a  5  percent,  solution  of  neutral  potato 
starch  by  boiling  800  c.c.  of  distilled  water  in  a  suitable  wide  mouth 
vessel ;  pour  into  it  milk  of  starch,  made  by  stirring  50  grammes  of 
starch  into  200  c.c.  of  cold  water,  and  boil  two  minutes. 
(3)  Iodine  Solution. — Place  1  gramme  of  iodine  and  2  grammes 
of  potassium  iodide  in  a  flask,  add  a  little  water,  say  5  c.c,  agitate 
until  dissolved  and  dilute  to  120  c.c;  or  dilute  50  c.c  tincture  of 
iodine,  U.S. P.,  with  50  c.c.  of  water,  containing  2  5  grammes  of 
potassium  iodide. 
Apparatus  Required. — (1)  One  quart  agate-ware  kettle;  (2)  one 
  *  . 
1  Lintner,  Jour,  fiir prak.  Chem.,  [2]  34,  378-394.  Junk,  Am.  Jour.  Pkar., 
55,  289  and  57,  13;  modified  in  Bulletin  of  Pharmacy,  February,  1898,  page52. 
