[ 187 ] 
VI. On the Variation loith Temperature of the Rate of a Chemical Change. 
By A. Veenon Harcouet, M.A., Hon. D.Sc. Oxon, F.R.S. 
With an Apjpendix 
hy William Esson, M.A., F.R.S., Savilian Professor of Geometry in 
the University of Oxford. 
Eeceived April 15,—Read May 9, 1912. 
In a study of the laws of connexion between the conditions of a chemical change and 
its amount, whose results have been communicated at intervals to the Eoyal Society, 
one of the conditions varied was the temperature of the solution in which the change 
took place.* 
On considering the numerical results, our first observation was that the increase of 
rate due to increase of temperature could be nearly represented for equal increments 
of temperature by a geometric progression. The rate was approximately doubled by 
each rise of ten degrees in the temperature of the solution. But the ratio of the 
series gradually diminished as the temperature rose, and a formula had to be found 
giving a series of this kind. For the way in which such a formula was found, see 
‘ Phil. Trans.,’ Series A, vol. 186, pp. 855-866. 
Using for the rate of change the symbol k, recently adopted by a committee of the 
Chemical Society, the formula was 
log kt 
log C+m log 
'273+ t 
273 ’ 
or 
C ^ / 273 + W ‘ 
k, \ 273 / ’ 
where k^ is the rate at 0° C., /q the rate at any other temperature t, and m a constant 
for each particular case of chemical change. 
This equation implies that at —273° C. the rate of change is nil. It has long been 
accepted that at this point, which is the zero of temperature, gases have no tension 
because molecules are at rest; and from our observations it appears that at the same 
point atoms are at rest and no contact between any kinds of matter brings about 
chemical change. 
The discovery by Esson of this natural law seems, as has happened in other cases, 
* ‘Phil. Trans.,’ vol. 156 (1865), p. 193; vol. 157, p. 117; and series A, vol. 186 (1895), p. 817. 
VOL. CCXII.-A 489. 2 B 2 Published separately, August 10, 1912. 
