The Effect of Liquid Media on the Grey Tin r harp over l White Tin Transformation in Commercially Pure Tin

Abstract

Dilatometric experiments using xylene, ethyl alcohol, alcoholic `pink salt' solution and distilled water show that the rates of transformation of the α → β and β → α reactions in tin are affected by the surrounding medium. The α → β rate for material which has undergone one previous β → α change is greater in water or ethyl alcohol than in xylene. All rates increase with temperature up to the highest investigated (29.86°C), and do not reach a maximum at about 25°C as reported by earlier workers. Alcoholic `pink salt' solution produces a much higher β → α transformation rate than other liquids in specimens which have undergone two successive transformations. The effects of xylene and ethyl alcohol during repeated transformation were studied at 30°C and 50°C; α → β rates were highest at the higher temperature. At 30°C, transformation rates increased with repeated transformation under xylene, but decreased under ethyl alcohol. It is suggested that xylene behaves as an inert liquid, while the effects observed with other liquids are due to the presence of a hydroxyl group. The increase of β → α transformation rate obtained with alcoholic pink salt is considered to be due to the reducing nature of the medium, and the formation of local electrolytic cells of various types. The results of certain earlier investigations are discussed on the basis of the present work.