[CONTRIBUTIOX FROM SOUTHERN
EXPERIMENT STATION, REGION v, BUREAUOF M I S E S , 5.s.DEPARTMENT O F TIIE
INTERIoR
A S D THE S C H O O L O F CHEMISTRY, UNIVERSITY O F .lLABAMA]
High Temperature Heat Content and Entropies of Hafnium Tetrafluoride and Rubidium Fluoride BY C. E. K'ZYLOR,G . E. W.~LDEN .IND DONALD F. SMITII I < E C E I V E D FEBRUARY
3 , 1959
hleasurenients of heat content.; abrive 273°K;. wcre conducted for hafnium tetrafluoride arid rubidium fluoride to tcniperutures of 1103 and 1199'K.. resuectivel\-. Xormal behavior \vas observed for both compounds. H e a t content equations twre derived a n d entropies ca1c;lated. ~
Introduction This paper presents the results of heat-content ineasureinents throughout the temperature range 273.15 to l190.0°K., with calculated entropies for hafnium tetrafluoride and rubidium fluoride. Data on these compounds in the range studied have not been published previously. Materials T h e 1iJftiiuiri tetrafluoride (supplied by the OCA Ridge S a t i o ial Ldboratoriei) was purified by sublimation under vacuum. Thereafter, spectrographic analysis2showed these inipurities: Zr, l.O%, with traces of Mg, ill, \.' and F e . The experimental results reported have not been corrected for impurities. Th: rubidium fluoride (also supplied by the Oak Ridge Sational Laboratories) was used as received. Impurities, determined were KF, 0.2');, NaF, 0.0001 'I,. T h e s&iplcs were enclosed in platiiium crucibles, the heat contents of which were determiued by separate rncasurririents. After filling with sample, the crucibles werc evacuated, filled with helium, evacuated t o approximately 10 m m .liclium pressure a i d sealed b~ platinum welding.
Measurements and Results Heat-content measurements were made in a Bunsen ice calorimeter of the type described in detail by Ginnings and Corruccini.3 The calibration factor for the unit, established electrically, was found to be 270.44 rt O.O(i joules per gram of mercury. =Idditional calibration tests on a synthetic sapphire sample, a t four different temperatures, yielded enthalpy values that checked accepted valuesi with less than 0. lsf;k deviation. The experimental procedure used in the calorimetric studies was as follows: A sample of approximately 1s g., sealed in the platinum container, was heated to an approximate predetermined temperature in a Marshal furnace designed so that i t could be shunted to obtain a region of uniform temperature, The temperature of the furnace was measured with a I)latinuni-platiriuiii lO(;G rhodium thermocouple previously calibrated against a National Bureau of Standards thermocouple. Once i t had been assured that the entire sample and container had reached the test temperature, the container was dropped into the calorimeter, the system closed and the heat evolved in cooling to 273.13'K. measured with the greatest possible o n manuscript cc,rnjrlete
