. Transactions. notice-able permanent change in both appearance and volume, which he sur-mised was caused by something other than ordinary thermal-expansion.*McBain and Joyner, employing a liquid dilatometer in the usual way. » Dental Cosmos (1895) 37, 661. 672 METALLOGRAPHIC PHENOMENA OBSERVED IN AMALGAMS located a sharp transition at ° C.^^ I have confirmed the existenceof this transition by means of two other entirely independent methodsof thermal analysis. Fig. 13 reproduces typical curves obtained by a modification of theRoberts-Austen method of observing temperature differences betwe
. Transactions. notice-able permanent change in both appearance and volume, which he sur-mised was caused by something other than ordinary thermal-expansion.*McBain and Joyner, employing a liquid dilatometer in the usual way. » Dental Cosmos (1895) 37, 661. 672 METALLOGRAPHIC PHENOMENA OBSERVED IN AMALGAMS located a sharp transition at ° C.^^ I have confirmed the existenceof this transition by means of two other entirely independent methodsof thermal analysis. Fig. 13 reproduces typical curves obtained by a modification of theRoberts-Austen method of observing temperature differences betweenthe sample and a neutral body while both were being heated simul-taneously in the same enclosure. It is evident that the transition isaccompanied by an appreciable absorption of heat. ^^ The heating curvesobtained with two cylinders packed for 8 min. under 141 and 1131 cir. cm., respectively, showed sharp peaks at essentially the sametemperature, which was close to ° C, corresponding to about the. 20 30 40 50 60 70 80°C. Fig. 14.—Transition region revealed by dilatometric method. Curvesrepresent heatings of same specimen on two successrve days. completion of the sudden drop in strength. The magnitude of the heatabsorption was somewhat greater with the cylinder packed at the lowerpressure, which also contained a greater proportion of mercury. Thebeginning and the end of the transformation are not sharply defined,but are in the neighborhood of 70° and 90°, respectively. On coolingfrom 100° to 50° no corresponding evolution of heat was observed, show-ing that the transition is not a reversible one. The absorption of heat,however, reappears at about the same temperature with each successivewarming of the same specimen; but the magnitude of the effect pro-gressively diminishes. Fig. 14 reproduces a pair of curves obtained by a method that dependsupon variations in linear thermal expansivity. The two curves show ^Ibid. (1912) 54, 649. i^McBain and Joyner {Ibid.
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