294 



Mr. G. F. Rodwell on the Effects of Heat 



figured in the above-mentioned paper. The measurements were made by- 

 means o£ a micrometer- screw. The expansions above the point of fusion 

 were determined by the method of the platinum cone described in the 

 previous paper. 



The alloys were made by fusing together in a porcelain crucible weighed 

 quantities of the iodide, bromide, and chloride of silver in such propor- 

 tions as furnished the five compounds described below. 



1. ChLORO-BEOM-IODIDE op silver having the COMPOSITIOTiT Aa I 



Br^ Ag^ Cl^, or Ag. I Br^ Cl^. 

 The alloy contains : — 



Agl .. 



. = 26-1692 



Ag . 



. = 60-1336 



Ag Br . 



. = 41-8708 



T 



, = 14-1435 



AgCl . 



. = 31-9600 



Br . 



. = 17-8176 







CI . 



. = 7-9053 





100-0000 





100-0000 



Specific gravity 6-152, when fused and cast into rods which were 

 allowed to cool in the air ; but when the rods were allowed to cool slowly 

 in hot parafiine, the specific gravity was found to be 6-066. The specific 

 gravity, calculated on the assumption that no change of volume takes 

 place, was found to be 5-836, showing a condensation equal to -0513 on 

 the calculated volume. Eusing-point 330° C. Specific gravity at the 

 fusing-point = 5-5118 ; at 750° C. = 5-057. The mass fused to a claret- 

 red liquid, which became brick-red, dull orange, and yellow as it coole(i, 

 and when cold had a brownish-yellow colour, a good deal resembling 

 bromide of silver. The mass contracted on solidifying, and formed a 

 substance with crystalline fracture, not perfectly homogeneous. A 

 small central core of less dense matter appeared near the upper end 

 of the rod, and was formed during the contraction of the mass. The 

 alloy gave a bright yellow powder, which turned green on exposure 

 to light. Loud harsh sounds were sometimes emitted during the cooling 

 of the mass. The substance was somewhat brittle, and broke as easily as 

 a rod of bromide of silver of the same dimensions. Heated in paraffine 

 to 250° C, it was found to be incapable of bending, and was as brittle 

 as when cold. In fracture and general characteristics it closely resem- 

 bled the bromide of silver. 



Placed in the expansion-apparatus the bar expanded regularly up to 

 125°-5C., and more rapidly than the chloride or bromide of silver; 

 between 125°-5 C. and 131°-5 C. a slight contraction took place ; at 131°*5 

 the mass began to expand again, and it expanded more rapidly than the 

 chloride or bromide ; at the melting-point and at 750° C, however, the 

 volume was nearly the same as that of the bromide. The following 

 results were obtained : — 



