﻿imparted 
  to 
  certain 
  Salts 
  by 
  Cathode 
  Rays. 
  199 
  

  

  IV. 
  Radioactivity 
  imparted 
  to 
  certain 
  Salts. 
  

  

  When 
  testing 
  a 
  salt 
  for 
  radioactivity 
  the 
  upper 
  part 
  of 
  

   the 
  electroscope 
  which 
  carried 
  the 
  measuring 
  system 
  was 
  

   detached 
  at 
  JF, 
  and 
  the 
  salt 
  placed 
  in 
  a 
  thin 
  layer 
  on 
  the 
  base 
  

   of 
  the 
  electroscope. 
  The 
  measuring 
  system 
  was 
  then 
  replaced 
  

   and 
  the 
  apparatus 
  made 
  air-tight 
  with 
  sealing-wax. 
  The 
  air 
  

   was 
  then 
  exhausted 
  to 
  a 
  pressure 
  of 
  15 
  mm. 
  of 
  mercury, 
  and 
  

   the 
  gold 
  leaf 
  was 
  given 
  a 
  charge 
  either 
  positive 
  or 
  negative 
  

   as 
  desired. 
  After 
  this 
  a 
  Bunsen 
  flame 
  was 
  applied 
  to 
  the 
  

   base 
  of 
  the 
  electroscope, 
  and 
  changes 
  in 
  the 
  charge 
  on 
  the 
  

   measuring 
  system 
  were 
  observed 
  by 
  noting 
  the 
  motion 
  of 
  the 
  

   gold 
  leaf. 
  

  

  A 
  list 
  of 
  the 
  salts 
  examined 
  in 
  this 
  way, 
  after 
  bombard- 
  

   ment 
  by 
  cathode 
  rays, 
  is 
  given 
  in 
  Table 
  1. 
  With 
  several 
  

   no 
  radioactivity 
  was 
  observed, 
  but 
  with 
  others, 
  such 
  as 
  the 
  

   sulphates 
  and 
  sulphides 
  of 
  a 
  number 
  of 
  the 
  elements, 
  a 
  

   radiation 
  was 
  obtained 
  which 
  discharged 
  the 
  measuring 
  

   system 
  when 
  positively 
  electrified. 
  In 
  no 
  case 
  did 
  this 
  radia- 
  

   tion 
  discharge 
  the 
  gold 
  leaf 
  when 
  negatively 
  electrified. 
  If 
  

   the 
  gold 
  leaf 
  was 
  charged 
  negatively, 
  then 
  on 
  heating 
  the 
  

   .salt 
  the 
  only 
  effect 
  was 
  a 
  slight 
  disturbance 
  of 
  the 
  leaf 
  due, 
  

   doubtless, 
  to 
  convection 
  currents. 
  If, 
  however, 
  the 
  gold 
  leaf 
  

   was 
  charged 
  positively, 
  no 
  effect 
  was 
  observed 
  until 
  the 
  salt 
  

   reached 
  a 
  certain 
  temperature 
  ; 
  the 
  leaf 
  then 
  began 
  to 
  fall, 
  

   and 
  continued 
  falling 
  with 
  a 
  rapid 
  and 
  regular 
  movement 
  

   for 
  a 
  few 
  minutes, 
  and 
  then 
  stopped 
  even 
  though 
  the 
  heating 
  

   continued. 
  

  

  Table 
  I. 
  

  

  

  

  Column 
  I. 
  

  

  Column 
  II. 
  

  

  Column 
  III. 
  

  

  Substance. 
  

  

  

  Gold 
  leaf 
  

  

  Gold 
  leaf- 
  

  

  Thermo- 
  

   luminescence. 
  

  

  

  

  positively 
  

   charged. 
  

  

  negatively 
  

   charged. 
  

  

  Manganese 
  Sulphate. 
  

  

  MnSO, 
  

  

  No 
  leak. 
  

  

  No 
  leak. 
  

  

  None 
  observed. 
  

  

  Zinc 
  , 
  , 
  

  

  ZnS0 
  4 
  

  

  55 
  ; 
  5 
  

  

  55 
  55 
  

  

  Faint 
  white. 
  

  

  Lead 
  „ 
  

  

  PbSO, 
  

  

  55 
  

  

  }) 
  

  

  None 
  observed. 
  

  

  Beryllium 
  ,, 
  

  

  BeS0 
  4 
  

  

  Leak 
  (small). 
  

  

  ,, 
  ,, 
  

  

  None 
  observed. 
  

  

  Calcium 
  „ 
  

  

  CaS0 
  4 
  

  

  Leak. 
  

  

  5? 
  55 
  

  

  Very 
  faint. 
  

  

  Strontium 
  „ 
  

  

  SrS0 
  4 
  

  

  >) 
  

  

  55 
  55 
  

  

  Faint 
  white. 
  

  

  Barium 
  ,, 
  

  

  BaS0 
  4 
  

  

  

  

  Faint 
  white. 
  

  

  Potassium 
  ,, 
  

  

  K,S0 
  4 
  

  

  >» 
  

  

  55 
  55 
  

  

  None 
  observed. 
  

  

  Calcium 
  Sulphide. 
  

  

  CaS 
  

  

  )> 
  

  

  5J 
  55 
  

  

  NoDe 
  observed. 
  

  

  Strontium 
  „ 
  

  

  SrS 
  

  

  55 
  

  

  55 
  55 
  

  

  None 
  observed. 
  

  

  Barium 
  ,, 
  

  

  BaS 
  

  

  

  5T 
  55 
  

  

  None 
  observed. 
  

  

  Calcium 
  Oxide. 
  

  

  CaO 
  

  

  No 
  leak. 
  

  

  )5 
  55 
  

  

  None 
  observed. 
  

  

  , 
  Calcium 
  Chloride. 
  

  

  CaCl 
  9 
  

  

  »> 
  j> 
  

  

  55 
  55 
  

  

  Faint 
  white. 
  

  

  Barium 
  ,, 
  

  

  Bad., 
  

  

  „ 
  ,, 
  

  

  

  Faint 
  white. 
  

  

  