272 
TEST  FOR  BROMIDES. 
decayed  in  the  interior,  sustained  vigorously  the  spreading  mass 
of  fleshy  branches  and  sword-like  foliage."  He  charges  the  de- 
struction of  this  famous  historical  monument  to  the  sheer  care- 
lessness of  the  Spanish  authorities,  who  might  have  prevented  it 
by  keeping  up  sufficient  props.  That  venerable  trunk  was,  it  is 
said,  as  hollow  and  about  as  large  in  the  year  1402  as  in  recent 
times  ;  and  the  hollow  had  even  then  been  used  immemorially  by 
the  Guanches  for  religious  rites.  The  age  of  6000  years  which 
has  been  assigned  to  it  by  some  of  the  "  most  sober  naturalists" 
may  not  be  very  greatly  exaggerated.  Probably  even  the  cavity 
was  as  ancient  as  the  oldest  of  California  Redwoods. — Am.  Jour. 
Set.  and  Arts,  March,  1868.    a.  g. 
TEST  FOR  BROMIDES. 
By  Surgeon  J.  H.  Bill,  U.  S.  Army. 
In  conducting  some  investigations  during  the  past  summer,  on 
the  physiological  relations  of  the  halogens,  it  became  absolutely 
necessary,  in  the  course  of  the  experiments,  to  devise  a  ready 
and  sensitive  test  for  bromine  in  the  presence  more  particularly 
of  chlorine. 
Any  analyst  will  bear  out  the  assertion — although  the  books 
make  light,  of  the  matter — that  it  is  a  difficult  thing  to  recognize 
traces  of  bromine  in  the  presence  of  excess  of  fhe  other  halogens. 
Thus  in  the  case  stated  above,  it  was  found  impossible  to  obtain, 
by  the  ordinary  methods  of  the  books,  a  certain  and  easy  recog- 
nition of  bromine,  when  chlorine  was  present. 
The  Fresenius  test  solution  of  auric  chloride  produces,  in 
faintly  acid  solutions  of  alkaline  bromides,  a  coloration  ranging 
from  dark  orange  red  to  light  straw  color,  according  to  the 
strength  of  the  solution.  Iodides  must  be  out  of  the  way.  Chlo- 
rides, however,  do  not  interfere  in  the  least.  The  following  is 
the  best  way  of  applying  the  test :  Separate  iodides  by  palladium, 
and  after  getting  rid  of  excess  of  palladium,  by  sulphuretted  hy- 
drogen, concentrate  the  solution  to  about  twenty-five  cubic  centi- 
meters. Select  two  test  tubes  of  the  same  size  and  shape  and 
color  of  glass.  Into  one  pour  the  solution  suspected  to  contain 
bromide.    Into  the  other  pour  pure  water,  adding  perhaps  a  trace 
