﻿23.— 
  A 
  NOTE 
  ON 
  THE 
  EFFECTS 
  OF 
  MERCUROUS 
  CHLORIDE 
  ON 
  

  

  CULICID 
  LARViE. 
  

  

  (Plates 
  XXIX-XXX). 
  

  

  By 
  S. 
  K. 
  Sen, 
  B.Sc. 
  

  

  Amongst 
  the 
  various 
  salts 
  experimented 
  with, 
  with 
  a 
  view 
  to 
  testing 
  

   their 
  effects 
  on 
  the 
  larvae 
  of 
  mosquitos, 
  mercurous 
  chloride 
  gave 
  some 
  

   interesting 
  and 
  rather 
  unexpected 
  results. 
  The 
  experiments 
  had 
  been 
  

   originally 
  designed 
  to 
  give 
  a 
  series 
  of 
  figures 
  in 
  respect 
  of 
  the 
  comparative 
  

   effects 
  of 
  salt 
  radicals 
  — 
  both 
  basic 
  and 
  acid 
  — 
  and 
  also 
  of 
  the 
  antagonistic 
  

   action,* 
  if 
  any, 
  of 
  those 
  salts. 
  But 
  on 
  a 
  preliminary 
  trial 
  the 
  results 
  

   obtained 
  with 
  HgCl 
  proved 
  to 
  be 
  of 
  sufficient 
  interest 
  to 
  warrant 
  follow- 
  

   ing 
  it 
  up 
  at 
  length 
  ; 
  and 
  this 
  seemed 
  all 
  the 
  more 
  desirable 
  in 
  view 
  of 
  the 
  

   possibilities 
  it 
  opened 
  up 
  as 
  a 
  larvicide 
  against 
  mosquitos. 
  Till 
  now 
  

   kerosine 
  has 
  practically 
  been 
  the 
  only 
  larvicide 
  in 
  use, 
  but 
  that 
  it 
  does 
  not 
  

   answer 
  the 
  requirements 
  of 
  an 
  ideal 
  larvicide 
  is 
  proved 
  by 
  the 
  attempts 
  

   that 
  are 
  still 
  being 
  made 
  by 
  various 
  workers 
  to 
  replace 
  it 
  by 
  a 
  more 
  

   convenient 
  and 
  less 
  expensive 
  material. 
  As 
  regards 
  HgCl, 
  sufficient 
  trial 
  

   has 
  not 
  yet 
  been 
  given 
  to 
  it 
  on 
  a 
  field 
  scale 
  to 
  justify 
  its 
  adoption 
  as 
  a 
  

   larvicide, 
  and 
  what 
  follows 
  is 
  presented 
  merely 
  as 
  an 
  indication 
  of 
  the 
  

   possibilities, 
  as 
  larvicides 
  against 
  mosquitos, 
  of 
  insoluble 
  salts, 
  non- 
  

   poisonous 
  to 
  human 
  beings. 
  

  

  The 
  preliminary 
  series 
  of 
  experiments, 
  which 
  aimed 
  merely 
  at 
  qualita- 
  

   tiv3 
  results, 
  were 
  conducted 
  with 
  exceedingly 
  minute 
  quantities 
  of 
  the 
  

   salt 
  taken 
  by 
  guess. 
  When 
  it 
  was 
  found 
  that 
  even 
  such 
  small 
  doses 
  

   produced 
  a 
  very 
  deleterious 
  effect 
  on 
  the 
  larvae, 
  quantitative 
  experi- 
  

   ments 
  were 
  taken 
  up 
  with 
  a 
  view 
  to 
  determining 
  the 
  lethal 
  dose. 
  In 
  

   view 
  of 
  the 
  very 
  small 
  solubility 
  of 
  HgCl 
  (0-002 
  gram 
  in 
  1 
  litre) 
  f, 
  any 
  

   possibility 
  of 
  osmotic 
  action 
  was 
  excluded, 
  and 
  the 
  assumption 
  was 
  con- 
  

   firmed 
  when 
  a 
  saturated 
  solution 
  of 
  the 
  salt 
  failed 
  to 
  kill 
  the 
  larva). 
  

   As 
  therefore 
  the 
  salt 
  presumably 
  acted 
  in 
  the 
  solid 
  state, 
  attempts 
  were 
  

   made 
  to 
  ascertain 
  the 
  minimum 
  quantity 
  of 
  the 
  salt 
  necessary 
  to 
  kill 
  the 
  

   larvae 
  in 
  relation 
  to 
  the 
  surface-area 
  of 
  water 
  (the 
  salt 
  particles 
  remaining 
  

   afloat 
  for 
  a 
  fairly 
  long 
  period), 
  as 
  the 
  action 
  of 
  the 
  salt 
  in 
  that 
  case 
  must 
  

   be 
  practically 
  independent 
  of 
  the 
  volume 
  of 
  water, 
  and 
  the 
  results 
  are 
  

   shown 
  in 
  Graph 
  1, 
  representing 
  varying 
  quantities 
  of 
  the 
  salt 
  in 
  relation 
  

  

  * 
  On 
  the 
  lines 
  adopted 
  by 
  Loeb 
  ; 
  vide 
  The 
  Dynamics 
  of 
  Living 
  Matter. 
  

   t 
  Found 
  out 
  by 
  conductivity 
  method 
  ; 
  Kohlrausch, 
  Z. 
  plysik 
  Ch., 
  50, 
  3(>5, 
  04-05 
  

   (quoted 
  by 
  Rpidell); 
  

  

  ( 
  184 
  ) 
  

  

  