Heat-capacity measurements and absolute entropy of ?-Mg₂PO₄OH

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• 作者：Catherine Leyx ^A1 ; J. Cornelis Van Miltenburg ^A2 ; Christian Chopin ^A1 ; Lado Cemi? ^A3
• 关键词：Adiabatic calorimetry ; DSC calorimetry ; Magnesium phosphate ; Heat capacity ; Entropy
• 刊名：Physics and Chemistry of Minerals
• 出版年：2005
• 出版时间：May 2005
• 年：2005
• 卷：78
• 期：2
• 页码：13-18
• 全文大小：292 KB

文摘

Abstract The low-temperature heat capacity of ?-Mg₂PO₄OH was measured between 10 and 400?K by adiabatic calorimetry. No phase transition was observed over this temperature range. A relative enthalpy increment of 22,119?J?mol^-1 and an absolute entropy value of 127.13¡À0.25?J?mol^-1?K^-1 at 298.15?K are derived from the results. The low-temperature heat-capacity data are compared with the DSC data obtained from 143?K to 775?K and show marginal differences in the common temperature range. The latter data are fitted by the polynomial % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX! % MathType!MTEF!2!1!+- % feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4qamaaBa % aaleaacaWGWbaabeaakiabg2da9maacmaabaGaaG4maiaaigdacaaI % 2aGaaiOlaiaaiAdacaaIYaGaeyOeI0IaaGOmaiaaiMdacaaI1aGaaG % 4naiaaykW7caWGubWaaWbaaSqabeaacqGHsislcaaIWaGaaiOlaiaa % iwdaaaGccqGHsislcaaI1aGaaGOnaiaaiodacaaIZaGaaGynaiaaic % dacaaMc8UaamivamaaCaaaleqabaGaeyOeI0IaaGOmaaaakiabgUca % RiaaiMdacaaI1aGaaGynaiaac6cacaaI1aGaaGynaiabgEna0kaaig % dacaaIWaWaaWbaaSqabeaacaaI1aaaaOGaaGPaVlaadsfadaahaaWc % beqaaiabgkHiTiaaiodaaaaakiaawUhacaGL9baacaqGkbGaaGPaVl % aabUeadaahaaWcbeqaaiabgkHiTiaaigdaaaGccaaMc8UaaeyBaiaa % b+gacaqGSbWaaWbaaSqabeaacqGHsislcaaIXaaaaOGaaiilaaaa!6CC9! $$ C_p = \left\{ {316.62 - 2957\,T^{ - 0.5} - 563350\,T^{ - 2} + 955.55 \times 10^5 \,T^{ - 3} } \right\}{\text{J}}\,{\text{K}}^{ - 1} \,{\text{mol}}^{ - 1} , $$ which allows extrapolation to high temperatures.