﻿1050 
  Dr. 
  Norman 
  Campbell 
  on 
  the 
  Electrical 
  

  

  ()'95xl0 
  -6 
  to 
  9*6 
  x 
  10" 
  6 
  mho. 
  cm. 
  and 
  the 
  conductivities 
  

   of 
  the 
  mixtures 
  prepared 
  from 
  them 
  increased 
  with 
  the 
  

   conductivities 
  of 
  the 
  alcohols. 
  But 
  no 
  relation 
  could 
  be 
  

   traced 
  between 
  the 
  conductivity 
  of 
  the 
  alcohol 
  and 
  the 
  

   " 
  purification 
  " 
  which 
  it 
  had 
  undergone 
  ; 
  the 
  specimen 
  with 
  

   the 
  highest 
  conductivity 
  had 
  been 
  twice 
  distilled 
  from 
  

   calcium, 
  while 
  the 
  original 
  sample 
  had 
  a 
  conductivity 
  little 
  

   greater 
  than 
  that 
  of 
  the 
  least 
  conducting 
  *. 
  The 
  effect 
  of 
  

   adding 
  2 
  per 
  cent, 
  of 
  water 
  to 
  the 
  least 
  conducting 
  alcohol 
  

   was 
  tried. 
  The 
  conductivity 
  of 
  the 
  alcohol 
  itself 
  was 
  appa- 
  

   rently 
  unaffected 
  by 
  the 
  presence 
  of 
  the 
  water 
  ; 
  such 
  a 
  result 
  

   is 
  to 
  be 
  expected, 
  for 
  the 
  conductivities 
  of 
  the 
  alcohol 
  and 
  the 
  

   distilled 
  water 
  used 
  were 
  nearly 
  equal 
  ; 
  but 
  the 
  mixtures 
  

   prepared 
  from 
  the 
  wet 
  alcohol 
  were 
  more 
  conducting 
  than 
  

   those 
  prepared 
  from 
  the 
  dry. 
  In 
  the 
  case 
  of 
  a 
  mixture 
  for 
  

   which 
  ?/ 
  = 
  - 
  12 
  the 
  increase 
  in 
  conductivity 
  was 
  45 
  per 
  cent. 
  

  

  It 
  must 
  be 
  remembered 
  that, 
  whether 
  the 
  mixture 
  were 
  

   "wet 
  " 
  or 
  " 
  dry," 
  prepared 
  from 
  pure 
  or 
  impure 
  alcohol, 
  the 
  

   current 
  through 
  them 
  obeyed 
  Ohm's 
  law 
  equally 
  well, 
  so 
  long 
  

   as 
  the 
  total 
  resistance 
  of 
  the 
  cell 
  containing 
  the 
  mixture 
  was 
  

   greater 
  than 
  10 
  8 
  ohms. 
  There 
  appears 
  then 
  to 
  be 
  no 
  special 
  

   advantage 
  in 
  taking 
  elaborate 
  precautions 
  to 
  purify 
  the 
  

   alcohol 
  used 
  ; 
  ordinary 
  commercial 
  absolute 
  alcohol 
  will 
  

   serve 
  as 
  well 
  as 
  any 
  other. 
  

  

  4. 
  Experiments 
  were 
  also 
  made 
  on 
  the 
  temperature 
  co- 
  

   efficient 
  of 
  the 
  conductivity 
  of 
  the 
  mixtures. 
  In 
  one 
  of 
  the 
  

   previous 
  papers 
  it 
  was 
  stated 
  that 
  the 
  variation 
  of 
  the 
  con- 
  

   ductivity 
  with 
  the 
  temperature 
  was 
  irregular 
  between 
  15° 
  

   and 
  10°. 
  This 
  observation 
  has 
  not 
  been 
  confirmed 
  : 
  a 
  per- 
  

   fectly 
  definite 
  value 
  for 
  the 
  temperature 
  coefficient 
  could 
  b 
  r 
  d 
  

   obtained 
  at 
  all 
  temperatures 
  between 
  0° 
  and 
  30°. 
  The 
  tem- 
  

   perature 
  coefficient 
  varies 
  with 
  the 
  temperature, 
  the 
  relation 
  

   between 
  the 
  conductivity 
  and 
  the 
  temperature 
  being 
  ex- 
  

   pressible 
  between 
  0° 
  and 
  30° 
  by 
  a 
  formula 
  of 
  the 
  form 
  

  

  y 
  = 
  y 
  (l 
  + 
  at4-bt 
  2 
  ). 
  

  

  For 
  mixtures 
  of 
  xylol 
  and 
  alcohol 
  for 
  which 
  y 
  is 
  less 
  than 
  

   0'25 
  both 
  a 
  and 
  b 
  are 
  negative 
  and 
  b/a 
  is 
  of 
  the 
  order 
  of 
  0'008. 
  

   For 
  alcohol 
  unmixed 
  with 
  xylol 
  a 
  is 
  positive 
  and 
  b 
  very 
  small 
  

  

  * 
  Dr. 
  Dawson, 
  to 
  whom 
  I 
  am 
  indebted 
  for 
  much 
  help 
  in 
  these 
  expe- 
  

   riments, 
  informs 
  me 
  that 
  it 
  is 
  now 
  believed 
  that 
  distillation 
  from 
  calcium 
  

   does 
  not 
  always 
  result 
  in 
  a 
  purification 
  of 
  the 
  alcohol. 
  The 
  water 
  may 
  

   be 
  removed, 
  but 
  other 
  impurities, 
  due 
  to 
  the 
  action 
  of 
  the 
  calcium 
  on 
  the 
  

   alcohol, 
  may 
  be 
  introduced. 
  I 
  was 
  unaware 
  of 
  this 
  fact 
  until 
  the 
  

   experiments 
  were 
  completed. 
  

  

  