Heretofore unpublished enthalpy data which were used in the derivation of smooth enthalpy and heat-.capacity data for NBS SRM 720 (a-A1, 2 0, heat capacity and enthalpy standard) are presented along with some details of the high-temperature experiments. Recent NBS low-temperature measurements on SRM 720 are smoothed by a least-squares spline technique and a revised table of certified values for enthalpy and heat capacity of a-Al,() from 10 K to near the meltng point (2250 K) is presented.

The relative enthalpy of NBS Standard Reference Material No. 781 (99.95 mass-percent pure, polycrystalline molybdenum: a metallic, hightemperature enthalpy and heat-capacity standard) has been measured with two differently designed, receivingtype calorimeters in the temperature ranges 273 to 1173 K and 1173 to 2100 K, respectively. The smoothed enthalpy data derived from these measurements are believed to have an inaccuracy not exceeding 0.6 percent at any temperature in these ranges. The heat capacity of Standard Reference Material No. 781 has also been measured in the temperature range 1500 to 2800 K using a millisecondresolution pulse technique with resistive self-heating. This technique measured, in addition, hemispherical total emittance. In this highest temperature range, the smoothed heat-capacity data are believed to be in error by no more than 3 percent. A complete description of all the NBS experimental techniques and a detailed analysis of all suspected sources of errors are presented.Equations representing the smoothed NBS enthalpy and heat-capacity data for SRM-781 molybdenum in the range 273.15 to 2800 K are presented along with a table of these data calculated from the equations at selected temperatures. A bibliography of all known publications on the enthalpy and heat capacity of molybdenum has been compiled. The NBS-measured enthalpy and heat-capacity data for molybdenum have been compared with those of all the principal investigators and compilers reported in the literature.

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