450 Mr. J. Crosby Chapman on Homogeneous 



the radiation from the plate as with that from the bromide 

 vapour. A plate of bromyl hydrate was also used in this way. 



It will be observed that the value of - obtained from the 



P 

 vapour has, within the limits of error, the same value as that 

 from the solid, thus showing that the two radiations are 

 identical in character. In order to find the nature of the curve 



connecting the atomic weights with -, in the neighbourhood 



of bromine the values of - for the radiations from selenium 



P 

 strontium, molybdenum, were determined. 



Element used as 

 radiator. 



Value of - for 

 P 

 radiatiun. 



Selenium 



18-5 

 11-1 



4-88 



Strontium 



Molybdenum 



Using these values combined with others known before to 



plot - against atomic weights, a smooth curve results, on 



P \ 



which the value of — for bromine lies, showing that the 



latter both in the solid aud vapour state gives out a 

 characteristic radiation the absorption coefficient of which 

 follows the law determined for solid elements. 



Radiations from Vajoour of Metliyl Iodide and from 

 Solid Iodine. 



The apparatus was similar to that used with the ethyl 

 bromide with the exception that, in this case, a quantity of 

 the iodide almost sufficient to saturate the space inside the 

 chamber was poured into an aluminium dish in the box ; 

 the filter pump and saturation bottle were dispensed with. 

 In addition the X-ray bulb was hardened by abstracting a 

 little air with the pump, in order that the rays given off 

 might excite the hard iodine radiation. 



The intensity of the rays from the ethyl iodide w 7 as very 

 much less than that from ethyl brqmide owing to only a 



