14 
Note  on  Lactic  Acid. 
f  Am.  Jour.  Pharm. 
(     January,  1911. 
IV.  An  aqueous  extract  of  the  drug,  prepared  without  heat. 
Each  of  these  preparations  was  given  to  a  dog  by  the  mouth, 
Nos.  I  and  II  in  amounts  of  i  gramme,  and  III  and  IV  in  consider- 
able quantity.  No  vomiting  or  modification  of  the  faeces  was  pro- 
duced, nor  could  any  other  sign  of  activity  be  detected. 
Although  the  potency  of  "  Blue  Flag  Root,"  in  the  fresh  state, 
is  evidently  well  estabHshed,  it  has  also  been  recorded  that  its  medic- 
inal activity  is  impaired  by  age.  From  the  results  of  the  above 
experiments,  it  would  appear  that  it  is  possible  for  the  drug  com- 
pletely to  lose  its  physiological  activity. 
A  NOTE  ON  THE  ASSAY  OF  LACTIC  ACID. 
By  Elias  Elvove. 
Hygienic  Laboratory,  U.   S.   Public  Health  and  Marine-Hospital  Service. 
Washington,  D.  C. 
It  has  been  pointed  out  by  Murray  ^  that  the  assay  requirement 
of  the  U.  S.  Pharmacopoeia  in  the  case  of  lactic  acid  (75  per  cent.) 
is  out  of  harmony  with  its  specific  gravity  requirement  since  a  mix- 
ture of  75  per  cent,  lactic  acid  and  25  per  cent,  water  has  a  specific 
gravity  of  about  1.175  at  25°  C,  whereas  the  U.S. P.  specific  gravity 
requirement  ("  about  1.206  at  25°  C")  would  correspond  to  a  mix- 
ture of  85  to  88  per  cent,  lactic  acid  and  12  to  15  per  cent,  water. 
It  occurred  to  the  writer  that  this  discrepancy  might  possibly  be 
due  to  a  weak  point  in  the  assay  method  which  may  cause  the  acid 
to  appear  weaker  than  it  actually  is.  This  further  suggested  the 
desirability  of  avoiding,  if  possible,  the  titration  of  the  acid  at  a 
boiling  temperature  as  called  for  by  the  present  U.S. P.,  since  the 
titration  at  a  boiling  temperature  instead  of  at  ordinary  temperature 
involves  not  only  comparative  inconvenience  but  is  also  more  liable 
to  yield  different  results  in  the  hands  of  different  operators. 
A  consideration  of  the  circumstances  of  this  case  appears  to  show 
that  it  is  possible  to  avoid  carrying  out  the  titration  at  a  boiling  tem- 
perature. For  it  is  quite  probable  that  the  object  of  the  boiling 
is  to  reconvert  into  acid  any  lactone  anhydride  which  may  be  present. 
And  since  it  is  known  ^  that  lactones  in  general  do  not  take  up 
water  by  mere  boiling  or  are  only  partially  converted  into  acid  by 
such  treatment,  but  are  converted  into  salts  of  the  corresponding 
^Merck's  Report,  N.  Y.,  16,  248  (1907). 
"Watts'  Dictionary  of  Chemistry,  vol.  iii,  p.  114  (1901). 
