■^DoimhiM-^^m^^     ^c^iV^  Principle  of  Suprarenal  Gland.  553 
unknown  samples,  it  was  considered  desirable  to  have  color  stand- 
ards which  were  certain  to  remain  unchanged  for  an  indefinite 
period.  A  casual  examination  of  the  pink  tint  produced  from  the 
epinephrine  base  by  boiling  with  potassium  iodate  solution  showed 
it  to  consist  of  a  mixture  of  red  and  yellow.  Unsuccessful  efforts 
were  made  to  find  a  particular  dye  which  would  yield  an  aqueous 
solution  corresponding  exactly  to  the  tint  in  hand ;  mixtures  of  dyes 
would  probably  serve,  but  a  better  source  was  found  in  the  color 
standards  adopted  by  the  committee  on  Standard  Methods  of  Water 
Analysis  of  the  American  Public  Health  Association,*^  viz.:  (a) 
platinum  solution  made  by  dissolving  20  gms.  K^PtClg  in  a  small 
amount  of  distilled  water,  adding  100  ex.  of  cone.  HCl,  and  diluting 
to  1000  c.c,  (b)  Cobalt  solution  made  by  dissolving  12  gms.  of 
C0CI2  6H2O  in  distilled  water,  adding  100  c.c.  of  cone.  HCl,  and 
diluting  to  1000  c.c.  By  mixing  these  two  solutions  in  approxi- 
mately the  proportion  of  i  of  the  former  to  3  of  the  latter  the  tint 
is  almost  indistinguishable  from  that  produced  from  the  epinephrine. 
The  intensity  of  this  color  standard  can  then  be  adjusted  by  dilu- 
tion to  correspond  exactly  with  that  obtained  by  mixing  5  c.c.  of 
the  1 :  5o,(X)0  solution  of  the  ash  free  active  principle  of  the  supra- 
renal (dissolved  with  the  aid  of  twice  the  calculated  amount  of 
HCl),  with  5  c.c.  of  a  0.2  per  cent.  KIO3  solution,  thus  yielding 
0.1  mg.  active  principle  per  10  c.c,  heating  just  to  the  boiling  point 
and  after  15  minutes  comparing  with  the  permanent  color  standards 
in  a  suitable  colorimeter.  After  standardization,  a  series  of  test 
tubes  may  be  prepared  with  dilutions  of  the  permanent  standard 
corresponding  to  o.oi,  0.02,  0.03,  0.04,  0.06,  0.08  and  o.io  mg. 
active  principle  per  10  c.c.  and  the  test  tubes  then  labelled  and 
sealed. 
Various  experiments  made  by  boiling  given  amounts  of  the  desic- 
cated suprarenal  glands  with  water,  dilute  HCl  and  mixtures  of 
these  with  0.2  per  cent.  KIO3  solution  indicated  that  the  principal 
difficulty  in  the  colorimetric  determination  is  caused  by  the  yel- 
lowish extractive  material  present  in  the  aqueous  solution  of  the 
sample.  This  in  many  cases  interferes  with  the  accurate  estima- 
tion of  the  intensity  of  the  pink  color,  and  therefore  leids  to  low 
results.  It  was  found  that  the  inconvenience  due  to  yellowish  tint 
was  greatest  when  a  larger  amount  of  sample  was  used  and  the 
Jour.  Infectious  Diseases,  Supplement  I,  p.  34,  May,  1905. 
