1?ptimTerPi9iT}  Assay  °f  U  S  .P .  Halogen  Compounds.  409 
The  following  result  was  obtained  by  the  above-described 
procedure  in  working  with'  an  ether-alcoholic  sodium  hydroxide 
mixture  containing  some  of  the  thymol  iodide  used  in  this  work, 
the  amount  of  which  was  unknown  to  the  writer  at  the  time  of 
working  with  it,  having  been  prepared  by  Dr.  Norman  Roberts  of 
this  laboratory  and  submitted  to  the  writer  as  an  "  unknown." 
Amount  of 
thymol  iodide 
given 
T*AgN03 
found  to  require 
^AgNOs 
as  calculated21 
Apparent 
iodine  content 
Gm. 
Q-4751 
c.c. 
16.88 
c.c. 
16.95 
Percent. 
45-°9 
From  these  results  it  would  seem  that  a  period  of  one  hour 
for  the  alkaline  boiling  and  another  hour  for  the  acid  boiling  should 
be  sufficient  for  most  practical  purposes  even  when  employing  as 
much  as  0.5  Gm.  of  the  thymol  iodide,  which  appears  to  be  a 
suitable  amount  to  take  for  the  assay. 
Public  Health  and  Marine-Hospital  Service. 
Hygienic  Laboratory,  Washington,  D.C. 
21  This  calculation  is  based  on  the  average  value  of  the  thymol  iodide  in 
terms  of  the  -^AgNOs  as  shown  by  the  results  given  in  Table  III. 
