on some Chloro-brom-iodides of Silver. 



303 



highly crystalline body (I speak of the iodide alone, not of the alloy) into 

 a transparent, plastic, denser body. What the precise function of the 

 molecular motion which disappears can be it is difficult to assume, since in 

 this case it not only changes the state of the body, but approximates its 

 molecules. 



Of the texture, specific gravity, Sfc. of the alloys. — It is noticeable that 

 when the percentage of iodide of silver is small, the alloy is brittle while hot, 

 and only slightly more tenacious than its constituents when cold (No. 1 ) ; 

 as the percentage of iodide increases, the alloy becomes somewhat less 

 brittle while hot, and considerably more tenacious, hard, and compact, 

 than any of its constituents (Nos. 2 & 3) ; while, when the percentage of 

 iodide becomes considerable (Nos. 4 & 5), the mass becomes extremely 

 plastic while hot, perhaps more so than the iodide itself, and very brittle 

 when cold. The specific gravity is in all cases above the mean of that 

 of the constituents ; it may be because the intercrystalline spaces of the 

 iodide are now filled with bromide and chloride. Thus, while the sp. gr. 

 of Ag CI is 5-505, of Ag Br 6-245, and of Ag I 5*675, that of the alloys is 

 as follows :— No. 1, 6-152 ; No. 2, 6-1197 ; No. 3, 6-503 ; No. 4, 5-9717 ; 

 and No. 5, 5-907 : while the percentage of the bromide, which alone has a 

 higher specific gravity than that of the alloys, in no case exceeds 42. 



In the accompanying curve table (p. 300) the expansion- curves of the 

 iodide and bromide of silver have been added for comparison with those 

 of the alloys ; the curve of chloride of silver has been omitted, because it is 

 almost precisely the same as that of the bromide. 



I have preferred to call these results " approximate " on account of 

 certain experimental difiiculties in the way of very precise determinations, 

 which difficulties I at present see no way of avoiding. 



