共查询到16条相似文献,搜索用时 80 毫秒
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提出一种测定溶液凝固点下降的新方法。将溶液和纯溶剂同时置于冷浴中,用半导体制冷块降温。用温度探头分别感应纯溶剂(R)、溶液(S)和冷浴(W)的温度:TR、TS和TW,并组成两个惠斯登电桥指示温差。当(TR-TS)-(TS-TW)出现最大值时,(TR-TS)为溶液凝固点下降值。本方法需要搅拌,降温速率以08—30K/min为宜。测定了萘苯溶液的凝固点下降值,苯中萘浓度20—700mmol/L时线性良好。 相似文献
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介绍了英国政府化学研究所(LGC)和兵总第204所样品的熔点和凝固点的准确测量方法,熔点和凝固点的测量结果,并进行了讨论。 相似文献
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低温型高精度凝固点测量装置及其应用 总被引:3,自引:1,他引:2
介绍了低温型高精度凝固点测量装置的设计研制、系统组成、性能特征、测量原理及其应用实例,并对所测3种有机物测量的扩展不确定度进行了详细的分析,结果表明,本装置对有机物凝固点的测量具有较高的精度和准确度。 相似文献
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利用△G=△H-T△S推导了稀溶液凝固点降低公式,根据形成溶液前后相变熵的改变,对公式的含义进行了解读,即凝固点的降低完全归结于溶解过程相比于熔化过程的熵变增加.并对公式的拓展应用进行了简要分析. 相似文献
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A method was proposed for calculating the thermodynamic properties, freezing point depression, boiling point elevation, vapor
pressure and enthalpy of vaporization for single solute electrolyte solutions, including aqueous and nonaqueous solutions,
based on a modified three-characteristic-parameter correlation model. When compared with the corresponding literature values,
the calculated results show that this method gives a very good approximation, especially for 1-1 electrolytes. Although the
method is not very suitable for some solutions with very high ionic strength, it is still a very useful technique when experimental
data is scarce. 相似文献
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Freezing curve-based monitoring to quickly evaluate the viability of biological materials subject to freezing or thermal injury 总被引:3,自引:0,他引:3
This paper is aimed at investigating the roles of freezing dynamics of a liquid droplet to characterize the properties of the material. In particular, freezing curve-based monitoring was proposed to quickly evaluate the viability of biological materials subject to freezing, re-warming, or other kinds of injury, which is an extremely important issue in practices such as cryobiology, hyperthermia, or freshness evaluation of bio-samples. An integrated micro analysis device was fabricated which is simple in structure and cheap to make. Preliminary freezing results demonstrated that minor changes in a biological material due to freezing or warming injury might result in a significant deviation of its freezing curve from that of the intact biomaterials. Several potential thermal indexes to quantify the material features were pointed out. Further, experiments were performed on some freezing and thawing processes of small amount of water on a cooling surface to test the effects of droplet sizes, measurement sites, cooling strength, and cooling geometry, etc., on the freezing responses of a water droplet. Their implementation in developing a new micro analysis system were suggested. This freezing curve-based monitoring method may open a new strategy for the evaluation of biomaterials subject to destruction in diverse fields. 相似文献
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Keitaro Kiyosawa 《Journal of solution chemistry》2004,33(4):323-328
The freezing point of mixtures of H2
16O with H2
17O was measured as a function of the molal concentration. The freezing points rose linearly with increasing molal concentration above that of pure ordinary water, H2
16O, at 273.15 K. This confirms Kiyosawa's previous conclusion [K. Kiyosawa, J. Solution Chem.
20, 583 (1991).], drawn from findings on changes in the freezing point of mixtures of H2
16O with H2
18O or D2
16O that even a difference in the number of neutrons in the hydrogen or oxygen atoms of water molecules makes them behave as different entities with respect to the colligative properties of solutions. This has been confirmed to also occur in mixtures of H2
16O with H2
17O. 相似文献
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In a recent article, Kiyosawa [J. Solution Chem. 33, 323 (2004)] reports that the freezing points of isotopic mixtures of ordinary water and 17O enriched water show an unexpectedly large linear dependence on the concentration of H217O. Surprisingly, the constant of proportionality to the H217O concentration is nearly five times larger than that of H218O found in earlier studies by Kiyosawa [J. Solution Chem. 20, 583 (1991)]. We show that the H217O result is not consistent with other data or models. For example, a recent determination of the triple point temperature
dependence on isotopic composition in naturally and artificially depleted waters [White et al. in Temperature, Its Measurement and Control in Science and Industry, Vol. 7, D. C. Ripple, Ed., AIP CP 684, 221–226 (2003)] is consistent with the H218O and D2O results from Kiyosawa (1991) [White and Tew in Report of the 22nd Meeting of the Consultative Committee for Thermometry, Document CCT/03-21, BIPM, Severes, France, 2003] but is inconsistent with the H217O results from Kiyosawa (2004). Additionally, the results from Kiyosawa (1991) are close to what would be found in ideal solutions
for those isotopic forms, whereas the H217O proportionality from Kiyosawa (2004) is about 10 times larger than similarly predicted. One possible explanation is that
the original 17O enriched water sample contained a small amount of D2O, and the sample, if available, should be subject to isotopic analysis to help resolve these inconsistencies. 相似文献
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Osmotic coefficients and activity coefficients of copper(II) chloride and cadmium chloride in aqueous solutions were evaluated from freezing point depression in dilute solutions of concentration range below 0.1 molal. The association constants for the ion-pairs, CuCl+ and CdCl+ were calculated as 2.3±0.3 and 74±5, respectively. 相似文献