832 
Color  Test  for  Oxalic  Acid. 
( Am.  Jour.  Pharm. 
(  November,  1920. 
the  action  on  a  frog  may  be  very  different  from  that  on  a  human 
being.  In  physiological  tests  no  attention  is  paid  to  the  age  of  the 
frog. 
6.  If  physiological  tests  are  not  thought  desirable,  is  a  chemical 
method  necessary  and  practicable?  Although  the  chemical  methods 
which  have  been  proposed  have  some  disadvantages,  it  seems  de- 
sirable that  a  standard  for  the  seeds  should  be  fixed  by  the  British 
Pharmacopoeia,  as  this  procedure  would  at  least  ensure  an  approxi- 
mately uniform  tincture. 
The  standardization  of  strophanthus  must,  therefore,  be  under- 
taken either  by  the  botanist,  the  physiologist,  or  the  chemist,  or  pre- 
ferably by  the  cooperation  of  all  three,  if  we  are  to  ensure  uniformity 
of  strength.  As  a  chemist,  I  am  strongly  in  favor  of  chemical  assay, 
and  a  review  of  the  processes  has  led  to  the  conclusion  that  Barclay's 
method  as  modified  by  Haycock  is  the  most  suitable  for  general 
adoption.  (See  Y.  B.  P.,  191 1,  p.  125.)  The  standard  I  would  sug- 
gest for  the  seeds  is  6  per  cent,  to  8  per  cent,  of  strophanthin  or  0.6 
per  cent,  for  the  tincture. 
COLOR  TEST  FOR  OXALIC  ACID.* 
By  Lewis  H.  Cheinoff 
denver,  colo. 
A  few  crystals  of  resorcinol  are  added  to  about  5  Cc.  of  the 
unknown  solution  in  a  test-tube,  and  the  mixture  is  warmed  slightly 
to  dissolve  the  resorcinol.  It  is  then  cooled  and  5  Cc.  of  cone,  sul- 
phuric acid  is  carefully  and  slowly  poured  in  along  the  side  of  the 
tube  so  as  to  form  a  layer.  A  blue  ring  will  be  formed  at  the  junc- 
tion of  the  2  layers,  if  oxalic  acid  is  present.  The  color  is  best  seen 
if  held  to  the  light  in  front  of  a  sheet  of  white  paper.  Care  must  be 
taken  that  the  mixture  does  not  warm  up  appreciably.  If  the  blue 
color  does  not  appear  in  a  few  minutes,  the  mixture  is  shaken  thor- 
oughly, and,  after  cooling  somewhat,  5  Cc.  more  of  sulphuric  acid 
is  added.  Should  the  color  still  fail  to  appear,  the  mixed  contents 
of  the  tube  should  be  gently  warmed  over  a  flame  (not  boiled)  when 
an  indigo  blue  color  will  diffuse  throughout  the  liquid.  If  the 
mixture  be  cooled  with  ice-water,  the  color  will  disappear  only  to 
*  Journal  Amer.  Chem.  Soc,  Sept. 
