568 
Progress  in  Applied  Science. 
(  Am.  Jour.  Pharm. 
t   December,  1915. 
the  sulphur  dioxide  was  oxidized  to  sulphuric  acid,  only  traces  being 
lost  through  escape  or  in  the  system.  The  lead  spiral,  the  author  points 
out,  however,  is  not  intended  to  replace  the  Glover  tower,  nor  to  do 
away  with  the  Gay-Lussac  tower. 
It  is  believed  that,  while  the  lead  spiral  will  take  considerable 
lead,  the  great  reduction  it  will  effect  in  the  chamber  space  will  make 
it  possible  to  construct  a  plant  with  considerably  less  lead  than  is 
required  in  the  ordinary  chamber  system. 
The  new  type  of  plant  requires  no  other  device  to  accelerate  the 
reactions,  occupies  much  less  ground  space,  and  would  not  need 
as  large  buildings,  and  therefore  should  decrease  the  initial  cost  of 
construction.  The  method,  however,  has  been  tried  only  on  a  labora- 
tory scale,  and  the  bulletin  refuses  to  predict  just  how  efficient  the 
commercial  plant  would  be,  but  states  that  all  indications  are  that 
this  method  offers  promise  of  being  economically  successful. 
Arsenate  of  Calcium  a  Promising  New  Insecticide. 
As  a  result  of  extensive  tests  during  1912,  1913,  and  1914  with 
different  insecticides,  the  entomologists  of  the  United  States  Depart- 
ment of  Agriculture  have  found  that  calcium  arsenate,  a  new  insecti- 
side,  gives  very  promising  results  in  the  control  of  certain  insects 
that  do  damage  by  chewing  on  fruit  trees.  Among  the  chewing 
insects  against  which  the  arsenate  of  calcium  proved  effective,  in 
laboratory  and  field  tests  conducted  at  Benton  Harbor,  Mich.,  are 
the  codling  moth,  the  fall  webworm,  the  tent  caterpillar,  and  the 
tussock  moth.  The  details  of  the  various  experiments  are  published 
in  Department  Bulletin  No.  278,  "  Miscellaneous  Insecticide  In- 
vestigations." 
In  these  tests  the  effects  of  arsenate  of  calcium,  both  alone  and 
combined  with  lime-sulphur  solution,  were  tested  in  comparison  with 
arsenate  of  lead  alone  and  in  combination  with  lime-sulphur.  The 
arsenate  of  calcium,  as  was  the  arsenate  of  lead,  was  used  at  the 
rate  of  2  pounds  to  each  50  gallons  of  water.  In  all  the  experiments 
the  arsenate  of  calcium  gave  very  satisfactory  results  in  killing  the 
larvae  without  burning  the  foliage.  In  a  number  of  cases  its  killing 
action  was  somewhat  slower  than,  but  compared  favorably  with,  the 
arsenate  of  lead.  Since  it  can  be  produced  more  cheaply  than  the 
lead  arsenate,  it  would  appear  to  have  distinct  value,  although  it 
has  not  been  sufficiently  tested  to  permit  recommending  it  unre- 
