10  Diastatic  Value  of  Malt  Extract*.      {Am  jJa0nuri^arrn- 
Amount  of  Amount  of 
No.  Extract.  Maltose  formed. 
1  0-5  giam  0  302  gram. 
2  10    "   0789  " 
3  1-5    "   1-877  ** 
In  the  last  of  these  experiments  only  three  times  as  much  extract  was 
used  as  in  the  first,  but  the  amount  of  sugar  formed  was  over  six 
times  as  great.  No  such  error  as  this  occurs  when  neutral  starch 
paste  is  used. 
In  arrowroot  we  have  a  starch  that  is  usually  neutral,  no  alkali 
being  used  in  its  extraction,  and  it  may  therefore  be  used  for  these 
determinations.  Distilled  water  should  be  used  for  making  the  paste, 
since  the  use  of  ordinary  water  may  introduce  a  very  large  error. 
The  following  method  is  suggested  for  the  determination  of  the 
diastatic  value  of  malt  extracts.  The  quantities  mentioned  can,  of 
course,  be  varied,  should  there  be  any  reason  for  so  doing;  but,  in 
general,  this  is  not  desirable,  as,  by  observing  these  details,  not  only 
will  correct  results  be  obtained,  but  they  will  be  directly  comparable 
to  those  obtained  by  other  observers  using  this  method.  In  this 
way,  some  of  the  discrepancies  that  occur  in  the  analyses  of  well- 
known  chemists  might  be  harmonized. 
A  3  per  cent,  starch  paste  is  made  by  adding  a  weighed  quantity 
of  Bermuda  arrowroot  to  distilled  water,  and  heating  the  mixture  to 
gelatinization  in  the  water  bath.  A  flask  containing  250  c0  c.  of  this 
paste  is  placed  in  a  water  bath  kept  at  55°C,  and  when  it  has  attained 
a  constant  temperature,  5  c.  c.  of  a  5  per  cent,  solution  of  the  extract 
in  distilled  water  is  run  in,  and  the  whole  mixed  by  shaking.  At 
the  end  of  half  an  hour  the  reaction  is  stopped  by  the  addition  of  two 
or  three  c.  c  of  a  10  per  cent,  solution  of  caustic  soda,  and  the  whole 
diluted  to  500  c.  c.  The  sugar  present  is  determined  by  Fehling's 
solution,  and  this,  minus  the  quantity  contained  in  the  extract  used, 
is  the  amount  formed  by  diastatic  action.  If  this  should  be  greater 
than  one-third  the  starch  used,  another  experiment  should  be  made 
with  a  smaller  quantity  of  extract.  The  sugar  should  be  calculated 
as  maltose  (reducing  power  =  §  glucose),  since  this  is  the  only  sugar 
formed  in  the  reaction. 
The  following  determinations  of  the  converting  power  of  two  well- 
known  malt  extracts  have  been  made  under  these  conditions.  In 
order  that  the  samples  examined  might  correctly  represent  the  ex- 
tracts as  supplied  to  the  whole  country,  they  have  been  obtained  from 
