. The London, Edinburgh and Dublin philosophical magazine and journal of science . t the temperatureof the room. Resistance of certain Am ilg a >ns with Temperature. 439 Curve A. The spiral was heated to 120° four times on oneday, and a cycle taken on the following day. The resistancestill falls with increasing temperature, but the part of thecurve representing this fall is nearer a straight line than inthe previous case. The most important feature is that at atemperature 63° there is a sudden fall in resistance insteadof an interval of temperature in which the resistance scarcelyalters, as
. The London, Edinburgh and Dublin philosophical magazine and journal of science . t the temperatureof the room. Resistance of certain Am ilg a >ns with Temperature. 439 Curve A. The spiral was heated to 120° four times on oneday, and a cycle taken on the following day. The resistancestill falls with increasing temperature, but the part of thecurve representing this fall is nearer a straight line than inthe previous case. The most important feature is that at atemperature 63° there is a sudden fall in resistance insteadof an interval of temperature in which the resistance scarcelyalters, as in the previous case. Also between 70° and 100°the heating and cooling parts of the curve coincide. Curve B was obtained after the spiral had been standing forfive weeks. It shows abrupt changes in direction at thepoints marked P, Q, R, corresponding to temperatures 37°,7-4°, and 27° respectively. At these temperatures thereforethe rate of variation of resistance with temperature is rapidlyaltering. Fu 3.—Resistance of an Amalgam containing- 239 per cent, of Zinc. a Q. In fig. 3 B represents the results obtained from an amalgamcontaining 23*9 per cent, zinc after it had been standing forseveral weeks. As it is typical of all the curves pertaining to amalgamscontaining more than 10 per cent, of zinc, which wereobtained after the spiral had stood for some time, its chiefpoints will be noticed. It starts with a portion MS, nearly a straight line, followedby a more sharply curved part SP. Along this latter part,when the experiments are in progress, the resistance does notattain its final value immediately the temperature of the bathhas become steady, but it has to stand in some cases fifteenminutes before a reading can be taken. At P, correspondingto a temperature 36°, there is a sudden change in temperature corresponding to this sudden change indirection is the same for all the amalgams which were triedhaving percentages of zinc higher than 95. Along PQ th
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectscience, bookyear1840
