108 Messrs. A. V. Harcourt and W. Esson. [May 9, 



May 9, 1895. 

 The LORD KELVIN, D.C.L., LL.D., President, in the Chair. 



A List of the Presents received was laid on the table, and thanks 

 ordered for them. 



The Bakerian Lecture was delivered as follows : 



BAKERIAN LECTURE. " On the Laws of Connexion between 

 the Conditions of Chemical Change and its Amount." By 

 A. VERNON HARCOURT, M.A., F.R.S., Student of Christ 

 Church, and Lee's Reader in Chemistry, and WILLIAM 

 ESSON, M.A., F.R.S., Fellow of Merton College, and 

 Deputy Savilian Professor of Geometry in the University 

 of Oxford. " III. Further Researches on the Reaction of 

 Hydrogen Dioxide and Hydrogen Iodide." Received 

 March 15, 1895. 



(Abstract.) 



In this paper are considered the effect upon the reaction of (1) 

 substances not directly participating in it, (2) temperature. 



A short description is given of the 'manner in which the observations 

 were made. 



The equation which expresses the result of a single set of observa- 

 tions was shown in a previous paper to be 



where y (l (H 2 0- + 2HI = P + 2H*0), 



and Vi(-ET 2 < 



are the amounts of potential change at the times t , t\ respectively. 



Each set of observations gives a mean value of , which is taken to 

 be the value of the rate of change under the conditions of the set. 



The effect of the variation of the conditions upon the value of a. is 

 considered to be a measure of their effect upon the course of the 

 reaction. 



Variation of Hydrogen Sulphate. 



It is shown from the results of three sets of experiments at tem- 

 peratures of 16, 20, and 30, that the increment in the value of the 



