Am,jan!!ifsSarm'}      Diadatic  Value  of  Malt  Extracts.  9 
acid,  with  constant  stirring.  Should  some  of  the  oxide  have  become 
hardened,  rub  it  into  powder,  and  gently  warm  the  mixture  until  per- 
fect solution  has  resulted.  Melt  the  stearic  acid  with  3J  troy  ounces  of 
the  petrolatum  and  then  gradually  add  the  rest  of  the  petrolatum. 
To  the  fused  mixture  now  add  the  mercuric  solution,  and  warm  the 
whole  on  a  water  bath  for  10  to  15  minutes.  Finally,  permit  the 
ointment  to  cool,  and  stir  it  occasionally  while  stiffening. 
ON  THE  DETERMINATION  OF  THE  DIASTATIC 
VALUE  OF  MALT  EXTRACTS. 
By  J.  R.  Duggan,  M.  IX,  Ph.D. 
The  following  suggestions  are  basel  on  some  recent  observations  I 
O  OS 
have  made  on  this  subject,  the  details  of  which  have  been  published 
in  the  American  Chemical  Journal,  Vol.  VII.,  No.  4.  As  these 
would  be  somewhat  tedious  to  the  general  reader,  only  the  more  im- 
portant conclusions  have  been  introduced  into  the  present  article. 
Many  of  the  determinations  of  diastase  in  malt  extracts  that  have 
been  made  heretofore,  are  undoubtedly  erroneous,  owing  to  the  fact 
that  certain  precautions  which  are  essential  to  correct  results  have  not 
been  generally  observed.  These  may  be  stated,  in  brief,  to  consist 
in  the  use  of  perfectly  neutral  reagents,  and  such  an  excess  of  starch 
that  not  more  thin  one-third  is  converted  into  maltose.  Moreover, 
the  extent  of  conversion  is  better  determined  by  the  amount  of  sugar 
formed,  than  by  the  time  required  to  show  a  certain  color  with  iodine. 
The  use  of  iodine  as  an  indicator  for  starch  in  the  presence  of  dex- 
trin is  very  unreliable,  the  color  produced  being  dependent  on  the 
amount  of  iodine  added,  the  temperature  of  the  solution,  and  various 
conditions  other  than  the  extent  of  conversion. 
All  of  the  commercial  starches  from  corn  or  potatoes  contain  more 
or  less  alkali  from  the  caustic  soda  used  in  their  extraction,  and  this 
cannot  be  entirely  removed  by  long  washing.  Determinations  made 
with  these  starches  show  a  great  diminution  of  diastatic  action,  owing 
to  the  retarding  influence  of  the  alkali.  This  in  some  cases  amounts 
to  as  much  as  90  per  cent.,  and  is  seldom  less  than  25  per  cent.  Not 
only  is  the  actual  error  considerable,  but  the  comparative  error  may 
be  almost  as  great.  The  following  table  shows  the  amount  of  sugar 
formed  by  varying  quantities  of  malt  extract  acting  on  an  ordinary 
laundry  starch : 
