process was el <1 or physical in its nal . If the rate 



of process in question was found to hare a temperature coeffi- 

 cient for 10 decrees between 2 and three, it was considered an 

 indication that the process was a chemical one or was controlled 



v " chemical reactions. If on the other hand the 10 degrse 



temperature coefficient proved to be much belcw ?, it was taken 

 as an indication of a physical reaction. In many discussions 

 of temperature influence en process rate it has been assumed 

 that if this coefficient appears to be more or less nearly cor- 

 stant and has a magnitude between 2.0 and 5.0, for the particu- 

 lar ranee studied, then the process follows the Van't Hoff-Arr- 

 henius ruli. If, on the ether hand, the coefficient is not 

 constant but varies greatly above or below this range of mag- 

 nitudes it is considered that the rule does not hold. This 



corrrocn, narrow interpretation of the Van't Koff-Arrhensis rule 



\14/ 

 (or R. £. T. rule as it is also called) appears to have >een 



based on a general misconception of t>ie Van't Hoff formula. 



15 

 As has been clearly pointed out by Stuar 4 ^ this formula itself 



makes clear that a constant coefficient is rot a part of the 

 rule, even for chemical reactions, and that Van't Hoff^nimself 



14 Reakticnsgeschwindigkeit — Temperatur - Repel 



if/ 



^-^ Stuart, C. P. Cohen, A study of temperature-coefficients 



Van't Hoff's rule. Ko - . ] Akademic van Wetenschappen to 

 Amsterdam Proceedings of the section of sciences of the Royal 

 Acad. Amsterdf . (Translate J ro i Verslagen van de Cewone 

 Vergaderingen der Wis-sn Nat ^rfcundige afdeelinrO 14 - 2nd part. 

 1153 - 1173. 1912. 



16 



Van't Hoff, J. 1T . , studies in Chemical Dynamics (Revised 



and enlarged by D. tfrnst Cohen and translated by Thomas Ewan) 



1896. 





