350 JOURNAI. OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 14 



(3) Isenkaumic or extrusive expansion, z. e*. at constant cnkaumy,^ or 

 constant heat content. 



These three methods were discussed and attention was called to the large 

 heating effects when liquids are expanded according to (3). Thus, water 

 by expansion through a porous plug from a little over 4000 atmospheres 

 should heat itself from 20 deg.' to 100 deg. C. 



Although the ordinary thermodynamic equations are applicable only to 

 fluids, at pressures far in excess of their ultimate strength solids fulfill to a 

 sufficient extent the condition of equality of pressure in all directions, and 

 therefore the equation for isenkaumic expansion may be applied to such 

 phenomena as the extrusion of wires and other solids through small openings. 



The paper was discussed by Messrs. White, Mueller, C. A. Briggs, and 

 Humphreys. 



The third paper, on Specific and latent heats of nickel and monel metal, was 

 presented by Dr. W. P. White, and was illustrated. 



The addition of heat makes all bodies hotter, but the amount of heat re- 

 quired to raise a body 1 degree is different for different bodies. This quantity 

 is the specific heat. It has important relations with the nature of atoms 

 and energy. The principal key to this relation was one of Einstein's earlier 

 discoveries. The specific heat at high temperatures is also of practical im- 

 portance in the treatment of metals, fire brick, and all materials which have 

 to be heated or cooled. An important economy in portland cement manu- 

 facture was effected some years ago by a recovery of heat based on a knowl- 

 edge of the specific heat of the cement at high temperatures. 



The simplest way to determine specific heat is to give a sample of the 

 material in question a known amount of heat by means of an electric heater, 

 measuring the change in temperature produced. This method works best 

 in a vacuum and at low temperatures where the heat losses are small. It 

 is almost the only method used at the low temperatures of liquid air and 

 liquid hydrogen. Its value at high temperatures is questionable, and it 

 has been little used. The irregularity which is unavoidable in most electric 

 furnaces and the very rapid rate of heat loss at such temperatures are both 

 difficulties. It is possible that by improved technique this method might 

 be used at high temperatures. If so, it would be a very interesting research. 



A more successful method at high temperatures is to heat a body in a fur- 

 nace and then drop it into a water calorimeter so that the most difficult 

 measurement, the measurement of heat, is carried out at room temperatures 

 with all the refinements of modern technique. The only thing to be done 

 in the furnace is then the heating of a body to constant temperature, for 

 which abundant time can be allowed. The greatest source of error is still 

 in the furnace, but this can be diminished if the distribution of temperature 

 within the furnace is carefully studied. If the material is a metal which will 

 oxidize in air it must be protected. One very ingenious method had been 

 the inclosing of the furnace in a high vacuum. A long tube, also evacuated, 

 led down into the calorimeter so that the body was in a vacuum from begin- 

 ning to end. In work at the Geophysical Laboratory, the metal specimens 

 were sealed up bulbs of sihca glass which held up to 1450° C, the melting 

 point of nickel, although they were somewhat soft at that temperature. Ordi- 

 nary glass would have run like molasses in April at this temperature. The 

 heat that may be lost in dropping the body through the air is not so serious 

 as might be supposed, but it cannot be neglected. This source of error was 



^ A proposed new term derived from the Greek Kavixa, heat. 



