the Chloride, Bromide, and Iodide of Silver. 291 



described in the case of the iodide bars. The coefficient of cubical 

 expansion for 1° 0. was found to be 



•000095454. 



Fizeau by his optical method found the coefficient to be -000098814. 

 The coefficient increases with the temperature, at least to the extent of 

 •000003 for each 100° C. increase of range. The expansion is considerable 

 in passing from the solid to the liquid condition, and between 350° 0. 

 and a temperature estimated at 750° C. I believe 350° C. to be near the 

 melting-point of the chloride. (Can the 260° C. which we see in books 

 be a misprint for 360° C. ? The chloride may be kept for any length of 

 time in a paraffine-bath at 300° C. without showing signs of fusion.) 

 The volume at — 60° C. has been taken as unity, in order that a better 

 comparison between the chloride and the iodide may be made in the 

 curve table, and an addition of '000003 to the coefficient has been 

 made for each 100° C. of temperature. Then, if we suppose a molten 

 mass of chloride of silver to be cooling from 750° C. to — 60° C, the fol- 

 lowing is an approximation to the volumes of the mass at the various 

 temperatures indicated : — 



Volume at 750" C = 1-177135 



„ 350 (liquid) = 1-116427 



„ 350 (soHd) . = 1-040302 



,,300 = 1-035082 



,,200 = 1-024937 



+ 100 = 1-015092 



= 1-005547 



,,-60 = 1-000000 



The specific gravity was found to be 5*505 in the case of a specimen 

 which had been often fused, and 5-405 in the case of a specimen which 

 had been once fused. This (former) would give 4-957 as the sp. gr. of 

 the molten chloride at the fusing-point. 



The chloride fuses to a dull light-red liquid, and becomes faintly 

 yellow when solidified, in thin layers colourless and quite transparent. 

 When cold it forms a pale dirty greenish-yellow solid, transparent in 

 thin layers. No sounds were emitted during cooling. The fracture is 

 crystalline. In thin layers the chloride is very flexible when cold ; and 

 when hot thick masses of it are very flexible. When cold it has a 

 decided metallic ring when struck. 



