On the Coefficients of Expansion, Sfc. 



549 



of Cubical Expansion and Contraction of the Alloy for 1° C. 



Between 0° and 118° = +"0000306 

 124 „ 128° C.= --0003240 



128 

 130 

 131 

 133 

 144 



130° = --0012990 



131° C.= - -0017330 



133° C.= - -0039000 



139° = - -0004329 



350° C.= + -0001150 



Plus has been placed before the coefficients of expansion on heating ; 

 minus before the coefficients of contraction. The expansion in pass- 

 ing from the solid to the liquid condition was determined as before. 



The coefficient between 144° 0. and the fusing point increased 

 rapidly with the temperature. 



If we take the volume at 0° C. as unity, we have the following 

 volumes corresponding to the temperatures given : — 



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 0. lower (viz., at 139° ¥.). 



4. The chlorobromiodides of silver also began to contract on heat- 

 ing (an effect which, of course, we must attribute solely to the pre- 

 sence 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 simultaneously propagated through the mass, prove that 

 violent molecular agitation is going on at such time as the iodide of 



