6o2 
Current  Literature. 
Am.  Jour.  Pharm. 
August,  1920. 
way  of  refinement,  and  this  property  is  the  essential  one  in  the  valua- 
tion of  diastatic  enzymes  applied  to  the  textile  industry.  The 
Lintner  method  for  measuring  the  saccharogenic  action  should  not 
be  used  for  comparative  studies  of  different  enzymes,  since  the  end 
products  are  not  the  same  in  all  cases.  Most  of  the  methods  hitherto 
employed  for  estimating  the  starch  liquefying  power  depend  on  the 
use  of  iodine  for  determining  the  end-point,  and  the  indications  are 
somewhat  arbitrary.  In  the  method  now  described  the  end-point 
taken  to  indicate  the  complete  destruction  of  the  starch  is  the  change 
of  the  opaque  starch  paste  into  a  clear  solution.  To  facilitate  the 
recognition  of  this  point  it  is  found  to  be  convenient  to  dye  the 
starch  with  neutral  red.  About  50  to  100  Gms.  of  dry  potato 
starch  in  a  large  porcelain  dish  are  wetted  with  100  Cc.  of  a  0.5  per 
cent,  solution  of  neutral  red;  the  starch  is  allowed  to  absorb  all  the 
color,  and  then  washed  repeatedly  with  water  until  the  supernatant 
liquor  remains  almost  clear.  The  dyed  starch  is  then  dried.  For 
the  test  a  2  per  cent,  starch  paste  is  made  by  stirring  the  colored 
starch  with  a  little  cold  water,  gelatinizing  with  boiling  water,  boiling 
for  ten  minutes,  and  making  up  to  the  required  volume.  The  paste 
is  introduced  in  portions  of  10  Cc.  each  into  large  test-tubes,  which 
are  then  placed  in  a  thermostat  at  40°  C.  When  the  correct  tem- 
perature is  reached,  increasing  quantities  of  the  diastase  solution 
are  added  to  the  tubes,  and  these  are  well  shaken  and  replaced  in  the 
thermostat.  The  end  of  the  reaction,  indicated  by  the  clearing  up 
of  the  color,  is  best  observed  by  comparing  the  liquefied  and  un- 
liquefied  tubes,  holding  the  tubes  in  the  light.  The  times  (T)  at 
which  the  various  tubes  become  clear  are  recorded  in  conjunction 
with  the  quantities  of  enzyme  solution  (E)  present,  and  it  is  found 
that  K  X  T  =  a  constant  K.  Then  if  F  =  enzyme  value  at  40° 
C;  D  =  dilution  multiple  of  the  original  enzyme  solution;  t  =  stan- 
dard time  (30  minutes);  E  =  quantity  of  diluted  enzyme  solution 
used ;  and  T  =  the  corresponding  time  of  liquefaction 
^  30  min.       D./  D./ 
Y   =    or  — 
40°  E.T.  K. 
In  this  way  the  results  may  be  checked  by  taking  the  average  of 
several  tubes  containing  different  amounts  of  enzyme.  The  method 
is  particularly  suitable  for  the  study  of  enzymes  which  have  a  starch 
liquefying  power  rather  large  in  comparison  with  the  saccharifying 
power,  as,  for  instance,  "Take-diastase."  (From  The  Analyst, 
April,  1920.) 
