HALOID COMPOUNDS OP SILVER, MERCURY, LEAD, AND COPPER. H49 
Volume at 0° C. * .=1-000000 
„ 118 =1-003610 
„ 124 =1-003610 
„ 128 =1-002314 
„ 130 .= '999716 
„ 131 .= ‘994517 
„ 133 .= -986717 
„ 139 .= -984120 
„ 144 .. . = -984120 
„ 150 .= ‘984810 
„ 300 =1-006500 
„ 350 (solid).=1-013790 
„ 350 (liquid).=1-024370 
In regard to this alloy the following points may be noted :— 
1. It possesses a similar density at three different temperatures. Thus, it is 
obvious that the density is the same at 0° C., at just below 130° C., and at 282° C. 
2. Although the alloy contains only 33*794 per cent, of iodide of silver, it contracts 
as considerably during heating as the iodide itself. 
3. While the iodide of silver commences its contraction at 142° C., and finishes it 
at 145°'5, the alloy commences to contract 18° C. lower (viz.: at 124° C.), and finishes 
6°*5 C. lower (viz., at 139° F.). 
4. The chlorobromiodides of silver also began to contract on heating (an effect 
which, of course, we must attribute solely to the presence of iodide of silver) at 
124° C., but they finished at 133° C. 
5. The harsh sounds emitted by the alloy during cooling, and the tremors simulta¬ 
neously propagated through the mass, prove that violent molecular agitation is going 
on, at such time as the iodide of silver is passing from the amorphous plastic condition, 
to the brittle crystalline condition, within the mass of the iodide of lead. 
6. The fusing point of the alloy is 177° C. lower than that of the iodide of silver, 
which constitutes one-third of its weight, and 33° C. lower than that of the iodide of 
lead, which constitutes two-thirds of its weight. 
7. If the lowering of the fusing point (also markedly apparent in the case of the 
chlorobromiodides of silver) is due to the fact that similar particles of matter attract 
each other more powerfully than dissimilar, and hence, when the particles of two 
bodies are mutually diffused, the attraction becomes less, and the molecular motion 
is consequently more readily assimilated, the same cause may serve to explain the 
commencement of the phase of contraction on heating the alloy, at a temperature 
18° C. lower than the substance to which it owes this property. 
8. It is interesting to compare one of the chlorobromiodides of silver with the lead- 
silver iodide. For this purpose we will take the chlorobromiodide which contains the 
nearest approach to the same quantity of iodide of silver as the alloy. The second of 
the chlorobromiodides before described (p. 1140) contains 41 "484 per cent, of iodide of 
