on some Chloro-hrom-iodides of Silver. 



303 



higlily crystalline body (I speak o£ 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 assame, since in 

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

 molecules. 



Of the texture, sjpecific 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 (iN'o. 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 : w^hile 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 difficulties in the way of very precise determinations, 

 which difficulties I at present see no way of avoiding, 



November 16, 1876. 



Dr. J. DALTON HOOKER, C.B., President, in the Chair. 



In pursuance of the Statutes, notice of the ensuing Anniversary 

 Meeting was given from the Chair. 



Dr. Henry Edward Armstrong and Capt. Greorge Strong Nares were 

 admitted into the Society. 



Prof. "W. Gr. Adams, Mr. Bramwell, Mr. Busk, Dr. Eussell, and Greneral 



VOL. XXV. z 



