Am.  Jour.  Pharm. 
July,  1880 
London  Purple. 
355 
-on  the  cotton  worm,  as  well  as  those  made  under  my  own  supervision, 
all  showed  that  its  effects  are  fully  equal  to  those  of  Paris  green.  Like 
the  latter  it  kills  the  worms  quickly  and  does  not  injure  the  plants,  if 
not  applied  in  too  great  a  quantity.  Farther,  it  also  colors  the  ingredi- 
ents so  as  to  prevent  their  being  mistaken  for  harmless  material.  Fin- 
ally, its  cheap  price  removes  the  temptation  to  adulterate  the  poison,  as 
every  adulteration  would  prove  more  expensive  than  the  genuine  article. 
It  is  even  superior  to  Paris  green,  as,  owing  to  its  more  finely-powdered 
condition,  it  can  be  more  thoroughly  mixed  with  other  ingredients  and 
'Used  in  smaller  proportion.  Experiments  on  a  large  scale  have  been 
made  with  the  dry  application  at  the  rate  of  2  lbs.  to  18  lbs.  of  dilu- 
ents, also  at  the  rates  of  i,  J,  \  and  \  lb.  to  18  of  the  diluents.  The 
last  proved  only  partially  effectual,  and  in  no  case  were  the  plants 
'injured  or  the  leaves  even  burned.  In  all  but  the  last  case  the  worms 
were  effectually  killed,  but  as  the  mixture,  at  the  rate  of  J  lb.,  was 
applied  with  greater  care  and  regularity  than  is  generally  had  on  a  large 
•scale,  and  also  in  very  dry  weather,  the  proportion  of  ^  lb.  to  18  of 
the  diluents  is  most  to  be  recommended.  All  higher  proportions  are 
simply  waste  of  the  material. 
Like  Paris  green,  it  is  not  soluble,  but  is  much  easier  kept  suspended 
in  water  than  the  former.  If  applied  in  this  way  some  care  has  to  be 
taken  in  stirring  it  in  the  water,  as  it  has  a  tendency  to  form  lumps, 
owing  to  its  finely-powdered  condition.  Experiments  on  a  large  scale 
with  this  material  diluted  in  water  gave  the  following  results  :  When 
•used  in  the  same  proportion  as  Paris  green,  namely,  i  lb.  of  the  poison 
to  about  40  gallons  of  water,  one  experimenter  reports  that  the  leaves 
were  slightly  crisped,  while  four  others  report  a  perfect  success  and  no 
injury  whatever  to  the  plant.  Experiments  bv  myself  and  Mr.  Schwartz 
showed  that  when  applied  in  the  proportion  mentioned  and  thoroughly 
stirred  up  in  the  water  the  leaves  were  partly  crisped,  though  by  no  means 
so  much  as  by  arsenic,  even  when  applied  in  weaker  solution.  When 
•used  in  smaller  proportion,  or  at  the  rate  of  }  or  J  lb.  to  40  gallons  of 
water,  it  did  not  burn  the  leaves  and  still  proved  effectual  in  destroying 
the  worms.  Repeated  experiment  on  a  smaller  scale  confirmed  these 
results  obtained  on  large  fields,  and  also  showed  that  the  proportion  may 
be  still  farther  reduced,  and  when  applied  with  great  care  and  in  very 
'dry  weather  \  lb.  to  40  gallons  will  kill.  Still  farther  reduction  in  the 
.proportion  of  the  powder  used  gave  negative  results.  I  would,  there- 
fore, recommend  the  use  of  J  lb.  of  this  powder  to  from  50  to  55  gal- 
