Societies and Academies

Abstract

LONDON. Physical Society, November 14.—Prof. S. P. Thompson, president, in the chair.—A paper on the theory of the aluminium anode, by W. W. Taylor and J.?.?. Inglis, was read by Mr. Inglis. Aluminium is very slowly acted upon by dilute sulphuric acid even at moderately high temperatures. With dilute hydrochloric acid, the action is violent, and it is found that if a little hydrochloric acid or soluble chloride be added to dilute sulphuric acid, the action is as violent as with hydrochloric acid of the same concentration. The object of the present paper is to find an explanation of this anomalous behaviour of sulphuric acid, and of the effect produced by the addition of chloride. It has long been known that, when an aluminium electrode is employed as anode in a solution of a sulphate or sulphuric acidj there is a very great resistance offered to the current, and that this resistance is due to a film which separates the electrode from the solution. If the aluminium is the kathode, or if other acids are substituted for sulphuric acid, this great resistance does not exist. It seems probable that the two phenomena are related, and that the film is also the cause of the slow action of sulphuric acid on aluminium. The authors have attempted to establish a theory which will explain these phenomena. The influence of certain salts of potassium in various concentrations was investigated, and the authors conclude that the presence of certain ions? enables a large current to pass through the cell. The reason' seems to be that the film of aluminium hydroxide with which the anode is covered is permeable to certain ions but impermeable to others. The anomalous behaviour in sulphuric acid would then be due to the impermeability of the film to the SO/' ions and also to the?? ions. Further experiments gave support to the view that the abnormal behaviour of aluminium anodes in sulphuric acid is due to impermeability.—A paper on a determination of the ratio of the specific heats at constant pressure and at constant volume for air and steam was read by Mr. Mackower. The method employed in this pap?ris similar to that used by Lummer and Pringsheim, and consists in allowing the gas under investigation to expand adiabatically and measuring the lowering of temperature caused by such expansion. The author's value for the ratio of the two specific heats in the case of air is 1.401. The observations with steam were similar to those in the preceding experiments, but special precautions were necessary to prevent the condensation of the steam in the tubes leading to the vessel. The results for steam were not sufficiently accurate to justify the application of corrections for radiation and for conduction and convection. The values of 7 deduced from two series of experiments were 1.307 and 1.304.