SummarySolubility data are provided and collected for the pure sodium and potassium soaps. Hydrolysis obscures the temperatures of solution but is obviated by the presence of a small excess of alkali. Each sodium soap has a large range of temperature between fair and high solubility, whereas the potassium soaps go abruptly into solution, at almost the same temperature and concentration of each soap.The only soaps that are even moderately soluble at room temperature are potassium laurate, myristate, and oleate, the potassium salt of acids from coconut oil, and the sodium oleate. The other sodium and potassium soaps of the saturated fatty acids require elevated temperatures for solution.Phase diagrams for the five commonest potassium soaps are developed and recorded.
No systematic study of the action of adhesives appears to have been published, although various isolated suggestions have been put forward from time to time. In the endeavour to find a rational approach to the study of these phenomena and the general factors upon which they are dependent we have carried out many hundreds of qualitative and quantitative tests with the most diverse materials and adhesives.It is our experience that joints are of two kinds; namely, mechanical and specific. Mechanical joints are possible only with porous materials, whereas specific adhesion occurs with smooth non-porous surfaces whether these are vitreous, polished or tiue crystal planes.We find that a joint results between porous materials whenever any liquid material solidifies in situ to form a solid film embedded in the pores. The most important and rather surprising example of a purely mechanical joint is wood joined with gelatin or glue, where apparently even adsoiption does.not occur.An excellent model of a mechanical joint is obtained by spot welding silver gauze to silver plates so that a porous surface is formed in which embedding can occur.Such surfaces are strongly joined by gelatin whereas smooth silver surfaces are joined but feebly. In mechanical joints the zone of the bedding is often the chief source of weakness.'The present investigation was undertaken for the Adhesives Research Committee of the Department of Scientific and Industrial Research and the authors are indebted to the Department for permission to publish the results. A more detailed account will be published by that Committee in their forthcoming Second Report.
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