JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. IV OCTOBER 19, 1914 No. 17 



PHYSICS. — The specific heat of copper in the interval 0° to 50°C., 

 with a note on vacuum- jacketed calorimeters.^ D. R. Harper 

 3d, Bureau of Standards. 



The determinations in the temperature range to 100° are inter- 

 preted to indicate that the specific heat of copper (hard-drawn 

 probably excepted) at 50° is between 0.0926 and 0.0931. 



The specimen of copper was a long annealed wire (50 meters) 

 99.87 per cent pure, suspended in vacuo and connected as part 

 of an electric circuit. A measured quantity of heat could thus 

 be imparted to it electrically and the temperature rise found by 

 using the specimen itself as a resistance thermometer. The test 

 specimen was thus its own calorimeter, no other substance being 

 included in the ''water equivalent" with the single exception 

 of a few grams of mica necessary for electrical insulation. To 

 arrange a large enough amount of copper in a form suitable for 

 the electrical measurements, the wire was coiled into spirals 

 containing about 150 cm. each and 32 of these, superposed with 

 mica plates between, built up a cyhnder about 10 cm. by 10 cm. 

 containing over 2 kgm. of copper and possessing an electrical 

 resistance of about 0.2 ohm, sufficient to permit of making the 

 necessary measurements with requisite accuracy. 



Potential leads tapped in at a distance from the ends of the 

 wire served to define a portion whose mass was that of copper 

 involved in the detemiination. The resistance of this portion 



1 To appear in the Bulletin of the Bureau of Standards, 11, 1914. 



489 



