- Email: [email protected]
Resistivity of pure silver; solid and molten
R E S I S T I V I T Y OF P U R E S I L V E R ; SOLID A N D MOLTEN.* BY
E D W I N F. NORTHRUP, Ph.D., Palmer Physical Laboratory, Princeton University. Member of the Institute.
TEE silver used in the measurements here recorded was very pure. It was given to the writer by Prof. G. A. Hulett from the supply which he is using in connection with his study of the silver voltameter. The writer takes this opportunity of expressing his very great indebtedness to Professor Hulett not only for supplying the silver for the measurements recorded here, but also for numerous courtesies and encouragements rendered the writer i n connection with his general research. The resistivity of the silver in the form of a soft drawn wire was determined between 2o ° C. and 6o ° C., using anoil-bath, mercury thermometer, and Kelvin double bridge. The same silver was then used in a container and measured as the temperature was slowly decreased and increased between I34 o° C. and 20 ° C. The manner of making the measurement and the apparatus used were the same as have already been described by the writer in this .IOUR~AL, in' the articles, " Resistivity of Copper in Temperature Range 2o ° C. to I45 °0 C." (January, I914), and " Resistivity of Pure Gold in Temperature-Range 2o ° C. to I5oo° C. '' (March, I914). While it has been the writer's custom to repeat the determination using a different container in each case and thereby check the precision of his results, this was not done in the case o f silver because of press of other investigations and because his increased familiarity with the method employed makes it entirely unlikely that any gross error has intruded. The results obtained are fully set forth in Curves I, II, and III, and in the table at the end of the article. Curve I is a plot of the resistivity of silver in the form of a soft drawn wire in the range 2o ° to 6o ° C. * Communicated by the Author. 85
86
E.F.
NORTHRUP.
[J.F.I.
Curve II is a plot of the resistivity in the range 20 ° C. to 134 °0 C. obtained in measuring the same silver in a container of magnesite 4 ° parts and alundum 60 parts. ' As has been explained in the articles referred to above, the portion of the curve which gives the resistivity in the solid state will be a little too high in the case o,f those metals which contract upon solidification, as is the case with silver. Curve III is a plot upon a larger scale than Curve II of the data obtained for molten silver. Curve I shows that in the range 20 ° C. to 60 ° C. the increase in resistivity with temperature is linear within the limits of accuracy of the measurement. It appears, however, from Curve II that over the wide range 20 ° C. to 96o ° C. the resistivity of silver in the solid state gives a curve which is slightly convex toward the temperature axis. The curve is, in this respect, the same as for gold and copper. At the moment of fusion the resistivity suddenly increases (which is the characteristic of all metals examined except bismuth and antimony, which contract on liquefying) from 8.5 to 16.6 microhms. The resistivity as shown by Curve II before fusion is, however, slightly too great on account of shrinkage in solidifying. Since the resistivity of the wire at 20 ° C. is 1.659, while the value obtained for silver which has cooled in the container is 1.749, it is thought that we should call the resistivity just before fusion 8.4. This would make the ratio of the resistivity just after fusion to the resistivity just before fusion 1.98. The points shown on the curves are those actually obtained. A few points which were in error, for obvious reasons have been omitted. It will be noted in Curve I I I that the slant of the two dotted lines which give the values obtained with rising and with falling temperature is not quite the same. The cause of this is not known with certainty, but it is supposed to be due to a lag of the temperature of the molten metal behind the temperature of the platinum v s . platinum + IO per cent. rhodium thermocouple used. The heavy line has been drawn as a mean. The departure from the mean at 960 ° C. is about o.6 per cent., which may be taken as the probable error in the measuremerits of the resistivity in the molten state. The measurement was not carried higher than 134 o° C. bee
E D W I N F. NORTHRUP, Ph.D., Palmer Physical Laboratory, Princeton University. Member of the Institute.
TEE silver used in the measurements here recorded was very pure. It was given to the writer by Prof. G. A. Hulett from the supply which he is using in connection with his study of the silver voltameter. The writer takes this opportunity of expressing his very great indebtedness to Professor Hulett not only for supplying the silver for the measurements recorded here, but also for numerous courtesies and encouragements rendered the writer i n connection with his general research. The resistivity of the silver in the form of a soft drawn wire was determined between 2o ° C. and 6o ° C., using anoil-bath, mercury thermometer, and Kelvin double bridge. The same silver was then used in a container and measured as the temperature was slowly decreased and increased between I34 o° C. and 20 ° C. The manner of making the measurement and the apparatus used were the same as have already been described by the writer in this .IOUR~AL, in' the articles, " Resistivity of Copper in Temperature Range 2o ° C. to I45 °0 C." (January, I914), and " Resistivity of Pure Gold in Temperature-Range 2o ° C. to I5oo° C. '' (March, I914). While it has been the writer's custom to repeat the determination using a different container in each case and thereby check the precision of his results, this was not done in the case o f silver because of press of other investigations and because his increased familiarity with the method employed makes it entirely unlikely that any gross error has intruded. The results obtained are fully set forth in Curves I, II, and III, and in the table at the end of the article. Curve I is a plot of the resistivity of silver in the form of a soft drawn wire in the range 2o ° to 6o ° C. * Communicated by the Author. 85
86
E.F.
NORTHRUP.
[J.F.I.
Curve II is a plot of the resistivity in the range 20 ° C. to 134 °0 C. obtained in measuring the same silver in a container of magnesite 4 ° parts and alundum 60 parts. ' As has been explained in the articles referred to above, the portion of the curve which gives the resistivity in the solid state will be a little too high in the case o,f those metals which contract upon solidification, as is the case with silver. Curve III is a plot upon a larger scale than Curve II of the data obtained for molten silver. Curve I shows that in the range 20 ° C. to 60 ° C. the increase in resistivity with temperature is linear within the limits of accuracy of the measurement. It appears, however, from Curve II that over the wide range 20 ° C. to 96o ° C. the resistivity of silver in the solid state gives a curve which is slightly convex toward the temperature axis. The curve is, in this respect, the same as for gold and copper. At the moment of fusion the resistivity suddenly increases (which is the characteristic of all metals examined except bismuth and antimony, which contract on liquefying) from 8.5 to 16.6 microhms. The resistivity as shown by Curve II before fusion is, however, slightly too great on account of shrinkage in solidifying. Since the resistivity of the wire at 20 ° C. is 1.659, while the value obtained for silver which has cooled in the container is 1.749, it is thought that we should call the resistivity just before fusion 8.4. This would make the ratio of the resistivity just after fusion to the resistivity just before fusion 1.98. The points shown on the curves are those actually obtained. A few points which were in error, for obvious reasons have been omitted. It will be noted in Curve I I I that the slant of the two dotted lines which give the values obtained with rising and with falling temperature is not quite the same. The cause of this is not known with certainty, but it is supposed to be due to a lag of the temperature of the molten metal behind the temperature of the platinum v s . platinum + IO per cent. rhodium thermocouple used. The heavy line has been drawn as a mean. The departure from the mean at 960 ° C. is about o.6 per cent., which may be taken as the probable error in the measuremerits of the resistivity in the molten state. The measurement was not carried higher than 134 o° C. bee