﻿546 
  Dr. 
  Meyer 
  Wilderman 
  on 
  Velocity 
  oj 
  Molecular 
  

  

  wound 
  to 
  a 
  spiral 
  on 
  a 
  lathe 
  supplied 
  with 
  small 
  hooks 
  

   and 
  used 
  instead 
  o£ 
  cords. 
  This 
  has 
  a 
  wonderful 
  flexibility, 
  

   gives 
  an 
  excellent 
  grip, 
  and 
  allows 
  good 
  adjustment, 
  if 
  

   required, 
  by 
  cutting 
  off 
  a 
  few 
  rings 
  or 
  by 
  forcible 
  stretching 
  

   of 
  a 
  few 
  of 
  them, 
  and 
  gives 
  always 
  the 
  same 
  constant 
  speed. 
  

   By 
  an 
  arrangement, 
  as 
  seen 
  at 
  C 
  of 
  the 
  photograph 
  (fig. 
  2), 
  

   the 
  same 
  spiral 
  can 
  be 
  used 
  for 
  the 
  different 
  pulleys. 
  

  

  (c) 
  Further 
  details 
  of 
  the 
  Method 
  (see 
  fig. 
  1, 
  PL 
  XVIII.). 
  

  

  The 
  beaker 
  with 
  1500 
  c.c. 
  of 
  the 
  liquid 
  was 
  kept 
  in 
  a 
  

   bath 
  of 
  a 
  constant 
  temperature, 
  a 
  1/10 
  degree 
  thermometer 
  

   having 
  been 
  immersed 
  in 
  the 
  liquid, 
  with 
  its 
  bulb 
  close 
  to 
  the 
  

   solid 
  block 
  ; 
  the 
  effect 
  of 
  stirring 
  upon 
  the 
  temperature 
  of 
  

   the 
  liquid 
  seemed 
  to 
  be 
  but 
  small, 
  but 
  had 
  to 
  be 
  adjusted 
  

   sometimes 
  by 
  the 
  temperature 
  of 
  the 
  outer 
  bath, 
  which 
  was 
  

   continuously 
  stirred 
  by 
  the 
  second 
  stirrer 
  driven 
  by 
  a 
  pulley 
  

   from 
  the 
  first. 
  In 
  case 
  of 
  substances 
  of 
  very 
  small 
  solu- 
  

   bility, 
  such 
  as 
  the 
  gypsums, 
  which 
  do 
  not 
  admit 
  sensitive 
  

   titration, 
  especially 
  since 
  very 
  dilute 
  solutions 
  had 
  to 
  be 
  

   investigated 
  here, 
  the 
  method 
  of 
  electric 
  conductivity 
  after 
  

   Kohlrausch 
  had 
  to 
  be 
  used. 
  Two 
  platinum 
  electrodes 
  (see 
  

   fig. 
  1) 
  were 
  fixed 
  in 
  the 
  ebonite 
  lid 
  of 
  the 
  beaker, 
  for 
  making 
  

   these 
  measurements, 
  the 
  electrodes 
  coming 
  into 
  the 
  middle 
  

   between 
  the 
  two 
  stirrers. 
  A 
  series 
  of 
  known 
  concentrations 
  

   of 
  the 
  same 
  CaS04 
  + 
  2H20, 
  which 
  later 
  on 
  had 
  to 
  be 
  in- 
  

   vestigated 
  as 
  a 
  solid 
  disk, 
  was 
  prepared, 
  and 
  small 
  intervals 
  

   of 
  concentrations 
  were 
  investigated 
  with 
  a 
  series 
  of 
  resistances, 
  

   and 
  so 
  a 
  scale 
  was 
  got 
  for 
  them 
  on 
  the 
  bridge, 
  for 
  the 
  same 
  

   temperature 
  and 
  speed 
  of 
  stirrer, 
  which 
  subsequently 
  was 
  

   used 
  when 
  the 
  solution 
  of 
  the 
  disk 
  was 
  investigated. 
  The 
  

   water 
  used 
  in 
  these 
  experiments 
  was 
  the 
  same. 
  The 
  volume 
  

   of 
  the 
  solution 
  remained 
  for 
  the 
  whole 
  series 
  the 
  same, 
  

   namely 
  1500 
  c.c. 
  

  

  In 
  case 
  of 
  other 
  substances, 
  such 
  as 
  benzoic 
  acid, 
  or 
  of 
  

   mixtures, 
  the 
  speed 
  of 
  reaction 
  was 
  measured 
  by 
  taking 
  out 
  

   samples 
  and 
  titrating 
  the 
  same. 
  The 
  samples 
  were 
  drawn 
  

   off 
  with 
  a 
  10 
  c.c. 
  pipette 
  through 
  the 
  glass 
  tube 
  fixed 
  in 
  the 
  

   ebonite 
  lid 
  of 
  the 
  beaker, 
  always 
  from 
  the 
  same 
  place 
  

   between 
  the 
  two 
  stirrers 
  ; 
  after 
  the 
  pipette 
  was 
  first 
  twice 
  

   filled 
  with 
  the 
  solution, 
  and 
  the 
  solution 
  let 
  back 
  into 
  the 
  

   beaker, 
  the 
  final 
  filling 
  of 
  the 
  pipette 
  for 
  titration 
  was 
  carried 
  

   through 
  within 
  the 
  last 
  5 
  to 
  10 
  seconds 
  of 
  the 
  minute. 
  

  

  Yery 
  great 
  and 
  quite 
  exceptional 
  precautions 
  had 
  to 
  be 
  

   taken 
  with 
  the 
  titrations 
  of 
  this 
  acid. 
  I 
  titrated 
  the 
  benzoic 
  

   acid 
  with 
  a 
  '088 
  normal 
  baryta, 
  back 
  titrating 
  the 
  same 
  with 
  

   a 
  '022 
  normal 
  benzoic 
  acid. 
  The 
  baryta 
  was 
  added 
  from 
  a 
  

  

  