Amjour,  Pharm.  |      Scientific  and  Technical  Abstracts  727 
small,  and  a  distance  of  100  meters  would  probably  be  sufficient  to 
ensure  safety,  particularly  if  the  cultivation  is  carried  out  with  late- 
flowering  species. 
Experiments  are  now  in  progress  with  the  view  of  ascertain- 
ing whether  the  cultivation  is  likely  to  be  financially  successful. 
SCIENTIFIC  AND  TECHNICAL 
ABSTRACTS 
Hydrogen  Peroxide;  Detection  and    Determination  of 
Traces  of  .  F.  W.  Horst.   Chem.-Zeit.,  192 1,  45,  572. — Traces 
of  hydrogen  peroxide  may  be  determined  qualitatively  and  quanti- 
tatively by  reduction  with  ferrous  sulphate,  and  colorimetric  estima- 
tion of  the  ferric  sulphate  formed  by  means  of  ammonium  thiocya- 
nate.  The  ferrous  sulphate  solution  must  be  freed  from  traces  of 
ferric  salt  by  passing  hydrogen  sulphide  through  it,  first  in  the  cold 
and  then  at  the  boiling  point,  and  is  cooled  in  a  current  of  carbon 
dioxide,  Twenty  cc.  of  the  sample  to  be  tested  is  placed  in  a  grad- 
uated tube,  and  a  few  cc.  of  petroleum  spirit  is  added  as  a  protection 
against  oxidation  during  the  reaction.  About  2  cc.  of  the  ferrous 
sulphate  solution  is  added  and  agitated  with  the  sample  by  means  of 
a  current  of  carbon  dioxide.  Five  cc.  of  air-free  ammonium  thiocya- 
nate  solution  is  then  introduced,  and  the  color  is  compared  with  that  M 
of  a  standard  solution. — W.  J.  W.,  through  J  own.  of  Soc.  of  Chem. 
hid. 
Ammonium  Sulphate  as  a  Weed  Killer. — Reporting  on  sul- 
phate of  ammonia  as  a  weed-killer,  the  Experimental  Station  of  the 
Rhode  Island  State  College  says  that  this  method  of  reducing  or 
eliminating  weeds  from  lawns  was  developed  there  by  a  series  of 
experiments  extending  over  twenty  years.  All  lawn  grasses  require 
in  order  to  grow  at  their  best  that  the  soil  be  supplied  with  plenty  of 
plant  food  in  the  three  elements  found  in  commercial  fertilizers — - 
nitrogen,  phosphorus  and  potassium.  Most  grasses  and  weeds  also 
require  that  the  soil  be  not  sour;  but  some  kinds  which  make  an 
even  turf  grow  well  in  an  acid  soil.   The  usual  fertilizers  employed 
