358 • TRANSACTIONS OF SECTION B. 



the same units. As possible sources of error in experimental determination 

 may be suggested : — 



(1) Effects produced by a layer of absorbed air or moisture, or both, between 



the mercury and the walls of the vessel ; 



(2) That the liquid (molasses mixture) into which the piston was dipped 



before insertion in the mercury is not completely removed; and 



(3) The unavoidable slip of the mercury past the piston. 



All these effects act in the same direction; i.e., they give rise to too great 

 a volume decrease, that is, to too high values of the compressibility. 



4. The Chemistry of the Glutaconic Acids. By Dr. J. F. Thorpe, F.R.S. 



5. The Influence of Constitution on the Molecular Volumes of Organic 

 Compounds at the Boiling Point. By G. Le Bas. 



6. The Influence of Substituents on Reaction Velocities. 

 By Professor R. Wegscheider. 



7. Report on the Influence of Carbon and other Elements on the Corrosion 

 of Steel. — See Reports, p. 83. 



FRIDAY, SEPTEMBER 1. 

 The following Papers and Reports were read : — 



1. Discussion on Indicators and Colour. 



(i) The Application of Methyl Orange for the Determination of the Affinity 

 Constants of Weak Acids and Bases, with a Discussion of the Errors. 

 By Dr. V. H. Veley, F.R.S. 



A brief account was given of the use of indicators, especially methyl orange, 

 for determining the affinity value of acids, as also of bases by the hydrolysis 

 values of their hydrochlorides. The advantages, limitations, and defects of 

 the method proposed were discussed in detail, and especial stress was laid upon 

 the fact that the method, though simple in its execution, is not intended to 

 supersede other methods of greater accuracy, available under like conditions. 

 The data of the hydrolysis, and affinity values deduced therefrom, are indepen- 

 dent of the more or less conflicting theories, namely, the ionic and chromophoric, 

 of indicators. Exception was more particularly taken to any correction of the 

 experimental results for the hydrogen ion concentration of the solutions, such 

 correction being based upon theoretical speculations based upon the former 

 theory, which has not met with universal acceptance. 



(ii) The Sensitiveness of Indicators. By H. T. Tizard. 

 See Reports, p. 268. 



2. Report on Dynamic Isomerism. — See Reports, p. 91. 



