1 144 
TABLE  4. 
Reaction. 
Reference. 
10 
(1)  Decomposition  of  ozone 
Perman  and  Greaves  (Proc.  Roy,  Soc. 
about 
1908,  80  A,  353) 
1.2 
(2)  SOa  + 0 ^ SOa 
1.36 
(3)  CO  + 0 CO2  1 
Bodenstein  and  his  pupils(Zeit.  Phys.  Chem. 
1903,  46,  725;  1905,  53,  166;  1907,  60,  1, 
1.40 
(4)  SOa  -^S0,  + 0 
46;  1911,  75,  30;  1912,  80,  148;  Zeit. 
Elektrochem.  1905,  11,  373;  Festschrift 
1.57 
(5)  NH3  N + 3H  1 
W.  Nernst,  1912,  p.  99. 
1.10 
(6)  H.  — 0 H2O 
1.18 
(7)  Decomposition  of  H2O3 
: Bredigand  Teletoff  (Zeit.  Elektrochem 
1.28 
1906,  12,  581) 
(8)  Cl  - ^ H-  ^ Cr-  -f  H 
JABLCZYNSKi(Zeit.  Phys.  Chem.  1908,  64,748) 
, 1.29 
(9)  Ti-  + H -^Ti  — + H 
Denham  (ibid  1910,  72.  641) 
1.29 
It  will  be  seen  at  once  on  glancing  at  the  two  tbregoing  tables 
tliat  in  the  ceactions  catalysed  by  solids  (with  the  exception  of  blood 
chai'coal)  the  temperatni-e  coëfficiënt  is  abont  1.3  i.e.  of  the  same 
order  as  that  for  diflfusion  ; whilst  in  ihe  case  of  reactions  catalysed 
by  colloidal  metals  and  enzymes  the  temperatnre  coëfficiënt  is  about 
2 i.e.  of  the  same  order  as  that  of  an  ordinary  Chemical  reaction  in 
homogeneous  medium.  How  is  this  difference  to  be  explained?  With 
catalysts,  which  canse  reaction  between  the  substances  in  queslion 
to  take  place  with  |)i-actically  infinite  velocity,  the  actnal  rate  of 
reaction  will  be  determined  solely  by  the  velocity  with  which  the 
reacting  substances  diffuse  to  the  surface  of  the  catalyst ; whether 
such  a catalyst  exists,  must  of  course  be  determined  separately  for 
every  case. 
Adsor|)tion  is  now  considered  to  be  an  exceedingly  rapid  process. 
If  the  reacting  substances  were  brought  to  the  surface  of  the  catalyst 
by  capillary  forces,  the  temperatui'e  coëfficiënt  would  correspond  to 
that  of  the  slower  process,  namely,  the  Chemical  change  involved. 
If,  on  the  other  hand,  the  reacting  substances  are  brought  to  the 
suilace  by  the  slow  process  of  diffnsion,  then  the  measnred  velocity 
would  be  that  of  a diffnsion  [)rocess  and  the  tem|)ei‘ature  coëfficiënt 
wonld  be  of  the  oi-der  of  1.3,  which  we  hare  seen  in  the  case  when 
solid  catalysts  are  nsed.  To  account  for  the  high  temperature  coëf- 
ficiënt in  the  case  of  reactions  catalysed  by  colloidal  substances  and 
enzymes,  one  might  suppose  that  the  Brownian  movement  of  these 
particles  acted  as  very  efticient  stirring  in  such  a way  that  the 
diffnsion  layer  was  removed  as  fast  as  it  was  formed,  with  the 
