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高温高压下电解质溶液热力学性质的研究不仅对探讨地球内部流体的作用具有重要意义，而且在很多实际工业过程中也都有广泛应用。本综述了近10年来高温高压下电解质溶液热力学参数的实验测量和理论计算的进展，实验设备还有待进一步的改进和完善，以获得更高温度和压力下的数据，理论计算不仅有待于实验的发展，也与溶液的结构理论密切相关。 相似文献
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Vegetation, microclimate, seedling frequency, freezing tolerance, and cold acclimation were compared for seedlings of Artemisia tridentata collected from 1775, 2175, and 2575 m elevation in the eastern Sierra Nevada, California. Data were used to test the hypothesis that ecotypic differences in stress physiology are important for seedling survival along gradients from desert to montane ecosystems. The vegetation canopy cover and A. tridentata seedling frequency were greatest at 2575 m, compared to 1775 and 2175 m. Snow cover ameliorated temperatures near the soil surface for part of the winter and depth varied across elevations. Freezing tolerance was compared for seedlings maintained in growth chambers at day/night air temperatures of 25°C/15°C. The temperature at which electrolyte leakage and Photosystem II function (FV/FM) from leaves were half-maximum was approximately −13·5°C for leaves of seedlings from all three elevations. Shifting day/night air temperatures from 25°C/15°C to 15°C/5°C initiated about 1·5° of acclimation by plants from all three altitudes, with seedlings from the highest elevation exhibiting the greatest acclimation change. Measurements of ambient air and canopy temperatures at the three elevations indicated that wintertime average low temperatures were consistent with the measured degree of freezing tolerance. At small spatial scales used in this study, pollen and seed dispersal between study sites may have precluded resolution of ecotypic differences. Patterns of freezing tolerance and cold acclimation may depend on a combination of mesoclimate and microclimate temperatures, canopy cover, snow depth, and snow melt patterns. 相似文献
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J. V. WALTHER 《Journal of Metamorphic Geology》1992,10(6):789-797
The equilibrium constant, K a , of the association reaction to form ion pairs from charged solute species in supercritical solutions can be calculated from a model based on published equations. Log K a at constant pressure is a linear function of the inverse in the dielectric constant of the fluid times temperature. The dielectric properties of H2 O and CO2 at supercritical pressures and temperatures can also be evaluated using the Kirkwood equation. Using Looyenga mixing rules, the dielectric constant of H2 O–CO2 mixtures can be obtained and the change in log K a with addition of CO2 in aqueous solutions evaluated. These changes in log K a with addition of CO2 are consistent with measured changes of log K a with addition of Ar in supercritical H2 O–Ar solutions.
Log Ka of KCl and NaCl increase to an increasing extent as the mole fraction of CO2 increases in H2 O–CO2 solutions. For instance, at 2 kbar and constant temperature between 400 and 600° C, log K a of KCl increases by about two orders of magnitude whilst that of NaCl increases by over four orders of magnitude as the CO2 mole fraction increases from 0.0 to 0.35. Such changes in log K a will have dramatic effects on the solubility of minerals in CO2 -rich environments. 相似文献
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用钾离子选择电极和银—氯化银电极构成的无液界电池测量了KCl+KHCO_3混合水溶液中KCl的平均活度系数,发现其活度系数的对数与混合溶液中KHCO_3的浓度m_2服从哈奈特关系式。用最小二乘法计算机处理求得了各离子强度条件下相应的哈奈特系数。还用适用于混合电解质溶液的皮茨公式计算了该体系电解质的平均活度系数和溶液的超额自由能,计算出活度系数与实验值之间的平均标准偏差为±0.006。溶液的超额自由能随溶液组成变化表明,对于有相同阳离子(K~+)的该混合溶液中离子间短程作用力主要受Cl~-作用的影响。用累代逼近法用微机计算,求得了KHCO_3~0的化学计量缔合常数经验公式及其热力学缔合常数。 相似文献
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Ice‐ and snow‐melted water flow over partially thawed frozen soil of cultivated slopes causes serious soil erosion, which results in soil degradation and affects productivity in Northeast China. Water flow velocity over frozen and nonfrozen soil shows importance in understanding meltwater erosion. In this work, a series of laboratory experiments were conducted to measure water flow velocity over frozen and nonfrozen soil slopes. Experiments were performed using the electrolyte trace method under the pulse boundary model, under conditions of 4 slope gradients (5°, 10°, 15°, and 20°), 3 flow rates (1, 2, and 4 L/min), and 7 sensors positioned at 0.1, 1.0, 2.0, 3.0, 4.0, 5.0, and 6.0 m away from the electrolyte injection point. Results showed that velocities over frozen soil slopes increased with flow rate and slope gradient. Flow velocities over nonfrozen soil slopes increased with flow rate and slope gradients from 5° to 15° and stabilized at 15°. Flow velocities over frozen soil slopes were 30%, 54%, 71%, and 91% higher than those over nonfrozen ones at slope gradients of 5°, 10°, 15°, and 20°. Flow velocities over frozen soil slopes under different flow rates of 1, 2, and 4 L/min were approximately 52%, 59%, and 79% higher than those over nonfrozen soil, respectively. This study can help in assessing the erosion of partially thawed frozen soil by meltwater flow. 相似文献
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实验研究了NaOH、HCl、NaCl和CaCl2等电解质加入量对蒙脱石悬浮液膨胀性的影响,并通过离子色谱、体视显微镜和激光粒度分析技术,研究了蒙脱石粒度变化与体积膨胀之间的关系。实验结果表明,NaOH、HCl对蒙脱石悬浮液膨胀性影响不明显,而NaCl和CaCl2对蒙脱石悬浮液的膨胀有明显的抑制作用;而且CaCl2对蒙脱石膨胀的抑制作用明显强于NaCl,CaCl2浓度比NaCl少了1个数量级时即可达到相同的膨胀抑制效果。离子色谱分析显示,CaCl2溶液与蒙脱石混合后,悬浮液上清液中的Ca2+浓度减少,而Na+浓度增加,分析存在离子交换过程。经激光粒度分析仪和体视显微镜观察,电解质的加入使颗粒之间产生了团聚作用,改变了颗粒的粒径,从而在宏观上表现为蒙脱石悬浮液体积的减少。 相似文献
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首次用新研制的高精密磁力浮沉子密度计测定ＮａＨＣＯ３，ＫＢｒ，ＫＮＯ３和Ｃａ（ＮＯ３）２在盐度为３０．０和３４．７温度为２９８、１０Ｋ时的偏摩尔体积（即ｐｍｖ）。重新测定了ＮａＣｌ，ＫＣｌ．Ｎａ２ＳＯ４和ＭｇＳＯ４在海水中的ｐｍｖ，并用实验精密验证了海水中主要电解质的ｐｍｖ的加和性关系。 相似文献
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黏度的研究对于流体流动的数字模拟、油气藏的开发以及CO_2的地质封存等都有着不可替代的意义,其也是评价油气藏的最终开发效果与反映油气藏经济效益的关键因素,当前关于电解质溶液黏度的理论研究主要存在2大类计算模型,即:(1)基于Erying绝对速率理论、Debye Hückel理论、Einstein方程等相关理论而开发的半经验半理论黏度模型;(2)基于如Jones Dole方程等的经验性黏度模型。 相似文献