Radioactive substances and their radiations - Tapa blanda

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 Excerpt: ...If the emanation again accumulates in the cold, as in the case described above, a second heating under identical conditions releases the same definite fraction of the emanation accumulated in the interval, but has no effect on the part which previously remained with the radium after the first heating. In most of the experiments of Kolowrat the effects of temperature were studied on a radium compound which had been initially fused, for in this way it was found possible to bring the compound back to the same physical conditions for a repetition of experiments. It is of importance to note that radium chloride with its water of crystallisation loses a greater part of its emanation at a temperature considerably below that of fusion. When once the water of crystallisation is removed, a much higher temperature at the second heating is required to drive off all the emanation. In this case, there is a considerable change in the physical and chemical state of the chloride after heating. There does not appear to be any evidence that the emanation is held in chemical combination with the radium, for neither radium nor radiferous barium are able to absorb again appreciably the emanation which has once been released. The general results indicate that radium compounds are very impervious to the escape of emanation, and that the liberation of emanation is due mainly to the process of diffusion, which is much facilitated by rise of temperature. If the process of escape is one of pure diffusion, it is to be expected that the amount of emanation released at a given temperature should be increased to some extent by increasing the fineness of division of the material so as to expose a large surface for the emanation to escape. In the case of thin films, another factor assists t...