﻿-570 
  Dr. 
  Meyer 
  Wildermau 
  on 
  Velocity 
  of 
  Molecular 
  

  

  give 
  us 
  A 
  Alabaster 
  : 
  A 
  Marienglass 
  = 
  2*5 
  : 
  1, 
  but 
  they 
  inform 
  

   us 
  that 
  the 
  surface 
  of 
  Marienglass 
  is 
  smooth, 
  the 
  surface 
  of 
  

   Alabaster 
  not, 
  and 
  when 
  we 
  polish 
  Alabaster 
  to 
  a 
  smooth 
  

   surface 
  the 
  constant 
  A 
  drops 
  to 
  half 
  its 
  value. 
  The 
  impression 
  

   is 
  thus 
  created, 
  that 
  the 
  constants 
  of 
  both 
  are 
  really 
  the 
  same. 
  

   Note 
  in 
  the 
  first 
  instance, 
  that 
  this 
  explanation 
  is 
  now 
  brought 
  

   forward 
  by 
  Bruner 
  and 
  Tolloczko, 
  who 
  were 
  the 
  first 
  to 
  find 
  : 
  

   " 
  The 
  important 
  argument 
  for 
  the 
  diffusion 
  theory 
  consisting 
  

   in 
  the 
  fact 
  that 
  corrosion 
  as 
  deep 
  as 
  1 
  mm. 
  has 
  no 
  effect 
  on 
  

   the 
  velocity 
  constant 
  ;" 
  that 
  they 
  no 
  longer 
  accept 
  this 
  state- 
  

   ment 
  in 
  case 
  of 
  Alabaster, 
  which 
  very 
  easily 
  gives 
  perfect 
  

   surfaces, 
  much 
  better 
  than 
  marble, 
  while 
  they 
  do 
  not 
  take 
  

   into 
  account 
  the 
  corrosion 
  of 
  all 
  other 
  substances 
  used 
  by 
  

   them, 
  which 
  are 
  not 
  able 
  to 
  give 
  such 
  smooth 
  surfaces 
  as 
  

   Alabaster, 
  but 
  for 
  which 
  they 
  nevertheless 
  furnish 
  us 
  with 
  

   perfect 
  and 
  impossible 
  constants, 
  under 
  conditions 
  when 
  the 
  

   substances 
  must 
  have 
  corroded 
  during 
  the 
  reaction 
  very 
  con- 
  

   siderably 
  ! 
  With 
  " 
  Platre 
  '^ 
  Bruner 
  and 
  Tolloczko 
  found 
  A 
  

   to 
  be 
  twice 
  as 
  big 
  as 
  that 
  of 
  Alabaster, 
  but 
  according 
  to 
  them 
  

   this 
  is 
  only 
  due 
  to 
  the 
  fact 
  that 
  some 
  substance 
  is 
  coming 
  off 
  

   from 
  the 
  sohd. 
  As 
  the 
  method 
  of 
  Bruner 
  and 
  Tolloczko 
  

   seemed 
  to 
  me 
  quite 
  unsuitable 
  for 
  a 
  reliable 
  investigation 
  

   here, 
  this 
  matter 
  had 
  to 
  be 
  investigated 
  again. 
  The 
  solu- 
  

   bility 
  of 
  the 
  Gypsums 
  is 
  only 
  about 
  2 
  gr. 
  per 
  litre, 
  and 
  some 
  

   of 
  the 
  solutions 
  and 
  differences 
  investigated 
  by 
  them 
  contained 
  

   no 
  more 
  than 
  '003 
  gr. 
  in 
  the 
  25 
  cc. 
  which 
  they 
  investigated. 
  

   Such 
  amounts 
  of 
  gypsums 
  Bruner 
  and 
  Tolloczko 
  wish 
  to 
  

   measure 
  quantitatively 
  either 
  by 
  evaporation 
  or 
  by 
  the 
  more 
  

   complicated 
  and 
  unreliable 
  method 
  of 
  precipitation 
  with 
  oxalic 
  

   acid 
  (collecting, 
  washing 
  the 
  same), 
  the 
  decomposition 
  with 
  

   SO4H2 
  and 
  titration 
  with 
  permanganate, 
  and 
  yet 
  they 
  supply 
  

   us 
  by 
  such 
  methods 
  with 
  constants 
  differing 
  in 
  a 
  series 
  only 
  

   by 
  about 
  2 
  per 
  cent. 
  ! 
  To 
  remove, 
  however, 
  all 
  possible 
  doubt 
  

   here 
  about 
  the 
  reason 
  for 
  the 
  difference 
  found 
  between 
  

   Marienglass 
  and 
  Alabaster 
  and 
  to 
  investigate 
  the 
  same 
  in 
  very 
  

   dilute 
  solutions, 
  when 
  the 
  surface 
  had 
  no 
  time 
  yet 
  to 
  corrode 
  

   except 
  but 
  very 
  little, 
  I 
  employed 
  the 
  method 
  of 
  electric 
  

   conductivity 
  as 
  described 
  in 
  paragraph 
  2, 
  which 
  enables 
  us 
  

   to 
  make 
  very 
  much 
  more 
  accurate 
  and 
  instantaneous 
  mea- 
  

   surements 
  than 
  it 
  is 
  possible 
  to 
  expect 
  from 
  the 
  methods 
  

   of 
  Bruner 
  and 
  Tolloczko, 
  and 
  very 
  great 
  care 
  was 
  taken 
  

   to 
  polish 
  the 
  surfaces 
  of 
  the 
  gypsums 
  as 
  perfectly 
  as 
  

   possible. 
  

  

  Table 
  III. 
  A 
  gives 
  the 
  speed 
  of 
  solution 
  of 
  the 
  following 
  

   Gypsums 
  CaS04 
  + 
  2H20: 
  — 
  Selenite 
  or 
  Marienglass 
  from 
  

  

  