322       Detection  of  Chlorine,  Bromine  and  Iodine.        { Am- j^^8h4arm- 
excess  of  iodide  over  that  of  the  bromide  present  in  the  solution  or 
mixture  to  be  tested,  or  if,  vice  versa,  the  bromide  be  in  excess,  then 
this  result  seems  to  follow  in  nearly  every  instance ;  viz.,  that  the  vapor 
of  that  halogen  which  is  present  in  a  very  small  quantity  relatively  to 
the  quantity  present  of  the  other  halogen  is  likely  to  be  overpowered 
by  the  vapor  of  the  latter.  When  relying  only  on  the  color  of  the 
vapor  it  was  found  that  when  the  proportion  of  the  iodine  to  the  bro- 
mide was  less  than  1  to  14,  the  iodine  could  not  be  detected,  and  even 
when  paper  moistened  with  starch  solution  was  used,  there  was  no 
indication  of  iodine  if  the  proportion  was  less  than  1  to  20.  As 
regards  detecting  bromine,  following  the  process,  and  relying  on  the 
color  of  the  vapor  only,  it  was  found  that  the  bromine  could  not  be 
detected  if  the  proportion  between  the  bromide  and  iodide  present  was 
less  than  1  to  15;  when  filter-paper  moistened  with  iodide  of  potas- 
sium and  starch  solution  was  used,  it  was  possible  to  detect  the  bromine 
so  long  as  the  proportion  between  the  bromide  and  the  iodide  is  not 
less  than  1  to  22. 
When  the  chloride  is  present  in  small  quantities  relatively  to  the 
iodide  and  bromide,  or  more  especially  if  it  be  the  bromide  which  is 
in  excess,  it  is  not  easy  to  detect  it  by  this  method ;  for  when  the  bro- 
mide is  in  large  excess  it  is  not  all  driven  off  by  the  addition  of  the 
dilute  sulphuric  acid,  so  that  when  the  strong  acid  is  added  the  remain- 
der comes  off  and  takes  along  with  it  the  chlorine. 
As  a  rough  way  of  detecting  the  presence  of  either  one  or  of  all  three 
of  the  halogens,  when  present  in  fair  quantity  relatively,  this  process 
will  answer,  more  especially  if  the  color  of  the  vapor  be  not  alone 
relied  on,  but  filter  paper  moistened  with  starch  solution  for  the  iodine 
and  with  iodide  of  potassium  and  starch  solution  for  the  bromine  be 
used.  i 
As  a  delicate  test  for  detecting  the  presence  of  small  quantities  of 
either  one  of  the  three  halogens  in  presence  of  the  other  two  it  is  not 
to  be  relied  on.—Phar.  Jour.  Trans.,  May  3,  1884,  p.  881. 
Phenic  Acid  in  Yellow  Fever.— Dr.  de  Lacaille,  of  Rio  de  Janeiro, 
professes  to  have  cured  thirty-eight  consecutive  cases  of  yellow  fever  by 
the  use  of  Declat's  preparations  of  phenic  and  sulpho-phenic  acids,  and,  in 
grave  cases,  the  phenate  of  ammonium.  In  the  early  stages  he  gives  the 
remedies  by  the  mouth,  but  in  the  advanced  stages  the  hypodermic  method 
is  necessary.  He  contrasts  very  favorably  his  recent  experience  with  his 
former  sad  failures  without  these  drugs. — Med.  and  Surg.  Rep.,  March  8. 
