was  coiitested  bj  Ericson-Auren  and  Falmaer ‘),  Tammann Marc ’), 
Sentkr  "),  Wiedermann *  *)  etc. 
Since,  accordiiig  to  the  diffnsion  tlieory,  in  Chemical  reactions 
which  occLir  merely  at  the  boundai'v  between  two  pliases,  tlie 
phenomenon  is  essentially  one  of'  ditfasion,  il  is  useless  to  (i’j  and 
determine  the  ordei-  of  reactions  from  Ihe  rate  at  which  they  proceed  ; 
this  method  of  argument  is  onij  applicable,  aecording  to  kinetic 
considerations  to  tlie  probablitj  of  collisions  in  liomogeneous  Systems 
and  loses  its  significance  when  applied  to  heterogeneons  systems. 
Moreover,  if  the  velocity  is  controlled  by  a diffnsion  process,  one 
will  get  a coëfficiënt  of  the  x elocity  similar  to  that  for  a nni-molecnlar 
reaction  and  the  coëfficiënt  will  be  indej)endent  of  the  actiial  order 
of  the  more  rapid  Chemical  reaction,  which  accompanies  the  process. 
Conseqnently  it  is  impossible  to  establish  a relation  between  the  ordei' 
of  a reaction  and  its  temperatnre  coëfficiënt  in  heterogeneons  systems. 
(a)  Temperatnre  coefjicients  of  u.ncMtalysed  reactions. 
Another  conseqnence  of  the  diffnsion  theoi'y  is  that  the  tempera- 
ture  coëfficiënt  for  an  elevation  of  KF  should  be  of  the  order  J .3  i.e. 
of  the  same  order  of  magnitude  as  the  temperatnre  coëfficiënt  of 
diffnsion  (compare  Ohölm®)).  We  shall  now  see  if  experimental 
results  confirm  this  inference  from  the  diffnsion  theory.  Thefollowing 
is  the  snmmary  of  resnlts.  (See  table  J next  page). 
These  resnlts  support  the  dift'usion  theory  of  reaction  velocity  in 
heterogeneons  medium.  In  this  connection  it  is  interesting  to  observe 
that  elevation  of  temperatnre  up  to  a certain  limit  is  found  to  be 
without  influence  on  the  decomposition  of  some  alcoholic  compounds 
by  sodium  amalgam  (Löwenherz,  Zeit.  Phys.  Chem.  1900,  32,480; 
1902,  40,  400)  and  on  the  velocity  of  dissolution  of  Casein  in 
alkalies  (Robertson,  Jour.  Phys.  chem.  1910,  14,  377). 
On  the  other  hand,  the  following  snmmary  of  results  shows  that 
the  conclusion  as  to  the  effect  of  temperature,  is  not  corroborated 
in  these  cases.  (See  table  2 next  page). 
It  has  already  been  pointed  out  that  velocities  of  ditfusion  only 
determine  the  rate  of  reaction  when  no  other  pi'ocesses  interfere 
and  specially  when  no  slow  processes,  taking  place  in  the  homogen- 
1)  Zeit.  Phys  Chem.  1906,  56,  689. 
2)  ibid.  1910,  69,  257. 
*)  ibid.  1908,  61,  385;  1909,  67,  470. 
9 Jour.  Phys.  Chem.  1905,  9,  311. 
“)  Zeit.  Phys.  Chem.  1909,  66,  445. 
8)  ibid.  1905,  50,  309;  1910,  70,  385. 
