jir'xs'^o"™- }  Chemical  Notes,  369 
iodine  as  chloride,  bromide,  or  iodide  if  these  elements  be  present.  A 
drop  of  the  alkaline  liquid  placed  upon  a  clean  silver  surface  will  at 
once  produce  a  black  stain  if  a  sulphide  has  been  formed,  whilst  the 
cyanogen  may  be  detected  by  the  Prussian  blue  test  in  a  portion  of  the 
liquid.  If  neither  of  these  is  present,  the  halogen  may  be  at  once 
tested  for  in  another  portion  of  the  solution  by  adding  nitric  acid  and 
silver  nitrate,  but  if  a  sulphide  or  cyanide  is  present,  it  must  be  first 
destroyed  by  mixing  the  solution  with  about  half  its  bulk  of  pure 
sulphuric  acid  and  heating  for  a  short  time  before  adding  the  silver 
nitrate. — Jour.  Chem.  Soc.^  May,  iSgO,  p.  348,  from  Gaz-zetta^  9,  574. 
The  Coloring  Matter  of  Sea-weeds. — Dyers  and  colorists  generally 
will  be  interested  in  a  paper  by  M.  Descourt,  read  at  a  meeting  of  the 
French  Academy  of  Sciences.  Attention  has  been  drawn  to  the  violet 
color  of  oysters  obtained  in  the  basin  of  Arcachon,  which  color  has 
been  attributed  by  some  observers  to  the  iodine  and  bromine  which  the 
water,  it  was  conjectured,  might  contain  in  excessive  proportion,  owing 
to  their  concentration  through  the  absence  of  rain  and  the  extreme 
dryness  of  the  months  of  June,  July  and  August.  M,  Venot,  an  oyster 
cultivator  of  Arcachon,  requested  M.  Descourt  to  endeavor  to  ascer- 
tain the  real  cause  of  this  coloring.  After  several  unsuccessful  researches 
M.  Descourt's  attention  was  attracted  by  a  noteworthy  circumstance. 
He  had  steeped  some  red  algae  in  a  little  of  the  sea-water  with  the 
object  of  studying  them.  Before  proceeding  to  analysis,  he  washed 
the  plants  in  distilled  water  in  order  to  clean  them  from  impurities.  To 
his  surprise  the  water  took  a  splendid  carmine-purple  tint,  which  was 
the  more  astonishing  as  the  sea-water  in  which  the  algae  had  been 
immersed  for  some  days  had  no  trace  of  discoloration.  A  more  com- 
plete examination  of  the  algae  and  of  the  colored  solution  enabled  M. 
Descourt  to  explain  the  peculiar  color  of  the  oysters.  Examined  under 
the  microscope,  the  fronds  of  the  algae  were  seen  to  have  a  mass  of 
spores  of  a  beautiful  carmine  color.  These  communicated  no  color  to 
the  natural  sea-water  of  the  basin  ;  but  when  the  latter  was  sufficiently 
diluted  it  took  from  the  spores  a  splendid  rose-color.  Treated  with 
alcohol  and  ether  a  beautiful  green  coloring  matter  similar  to  chloro- 
phyll was  obtained.  Treated  with  distilled  or  fresh  water  a  magnifi- 
cent carmine-purple,  slightly  fluorescent,  was  produced.  M.  Descourt 
therefore  concluded  that  the  color  of  the  oysters  was  due  to  the  pres- 
ence on  the  breeding-ground  of  a  large  quantity  of  these  small  algae 
which  belong  to  the  beautiful  rhodospermae  or  Floridae  families,  genus 
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