半导体凝固点测定仪的研制及其应用

为了配合物理化学实验“凝固点降级法测定萘的摩尔质量”,研制出半导体制冷凝固点测定仪,实现了凝固点测定和摩尔质量计算的自动化,解决了老式实验装置存在的问题。通过对环己烷凝固点和萘摩尔质量的测定,验证了该仪器的可靠性,同时还探讨了搅拌速率和冷阱的温度变化对凝固点测定值的影响。     

凝固点降低测定物质摩尔质量实验装置的改进

介绍一种改进的凝固点降低法测定物质摩尔质量的实验装置,通过调节合适的阻凝温度与散热补偿电流,对样品凝固点的测定精度可以达到±0.003℃,对样品摩尔质量的测定误差可控制在0.5%左右。     

第5届全国大学生化学实验邀请赛(试卷C1)实验C1 凝固点降低法测定未知物的摩尔质量

一、实验目的 (1)掌握凝固点降低法测定物质的摩尔质量的基本原理与实验技术. (2)测定水的凝固点降低值,计算未知物的摩尔质量.     

凝固点降低法测定摩尔质量实验装置的改进

对凝固点降低法测定摩尔质量的实验装置进行了改进。改进后操作简单,所得结果准确。     

介绍一个绿色物理化学实验——凝固点降低法测定葡萄糖的摩尔质量

以葡萄糖-水为体系对传统的凝固点降低法测定摩尔质量实验进行了改进,以低温小钢珠代替晶种,建立了一种控制过冷深度的有效方法;利用干燥的方法解决了葡萄糖样品中结晶水不确定的问题。     

凝固点降低法测定摩尔质量实验方法改进

以差示扫描量热法（DSC）测定环己烷溶液的凝固点降低值。在降温速率1℃·min^-1、氮气气氛下,测定了叔丁醇和甘油的环己烷溶液的凝固点降低值,计算了两种物质的摩尔质量,误差在10％之内。     

凝固点降低法测定摩尔质量实验改进

用改进的凝固点测量管 ,在 - 5℃和 - 1℃双温冷却剂中测量葡萄糖等物质的摩尔质量 ,比其他方法操作简便 ,所测的表观摩尔质量值更接近实际值     

第5届全国大学生化学实验邀请赛(试卷C3)实验C3 粘度的测定及应用

一、实验目的(1)掌握用乌氏粘度计测定粘度的方法。(2)测定一未知高聚物的平均分子量。二、实验原理及实验内容1实验原理高聚物是由单体分子经加聚或缩聚过程而合成的,其聚合度不一定相同,一般高聚物是摩尔质量大小不同的大分子混合物,摩尔质量常在103~107之间,通常所测的高聚物摩尔质量是一个统计平均值。高聚物溶液的粘度是它流动过程中内摩擦力的反映。粘度比较大是高分子溶液的基本特征之一,并且其特性粘度与平均摩尔质量有关,可利用这一关系测定其摩尔质量。有关粘度的定义式如下:相对粘度ηr:ηr=ηη0(1)式中,η为高聚物溶液的粘度,…     

步冷曲线法——对凝固点降低测定摩尔质量的改进

要测量溶剂和溶液的凝固点之差,对于纯溶剂如图1(a)所示,凝固点是在一定时间内固定不变。但对于溶液,除温度外还有溶液浓度的影响。当晶体生成,放出的凝固热使体系温度回升,由于不断析出溶剂晶体,溶液的浓度逐渐增大,凝固点会逐渐降低。因此,凝固点不是一个恒定值。以前通常把回升到最高点的温度作为凝固点,由于这时已有溶剂晶体析出,所以溶液浓度已不是起始浓度,该凝固点也已不是原浓度的凝固点。由图1(b)可以看出,这时的凝固点比实际凝固点要低,以此数值计算出的ΔTf要大于真值,最后计算出的摩尔质量要小于真值。建议测出步冷曲线,按图1(…     

液态己烷摩尔质量、分子式的确定

在中学化学实验中使用维克多·迈耶( Victor Meyer)装置来对有机物的摩尔质量加以确定,无论是在教师的演示实验、还是在实验室的学生型实验都在时间、仪器准备等方面难以实现。本实验通过一种简易装置,对液态己烷在摩尔质量方面的测定作了探讨;并由此进一步对其分子式加以确定。这对学生加深对阿伏加德罗定律的认识以及对有机化合物在分子式方面的认识将起到十分重要的作用。     

Neutral diterpenoids of oleoresins of five species of conifers of Transcarpathia

The compositions of the neutral diterpenoids of the oleoresins of five species of conifers growing in the Transcarpathia have been studied. It has been found that the oleoresins ofAbies alba M.,Larix decidua M., andPicea excelsa L. contain more than 50% of neutral diterpenoids. The group and qualitative compositions of the oxygen-containing diterpenoids have been determined. In the oleoresins ofAbies alba,Picea excelsa, andPicea abies tertiary alcohols — cis-abienol and isocembrol — predominate, while inLarix decidua the main component is the hydroxy ester larixyl acetate. Primary alcohols related to the resin acids have been found in all the oleoresins investigated. Features of the distribution of diterpenoids according to the species of conifers have been revealed. The results obtained are necessary for the chemotaxonomy of conifers of the family Pinceae.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodynkh Soedinenii, No. 6, pp. 812–816, November–December, 1988.     

利用手持技术改进测定乙醇分子结构实验

利用压强传感器代替排水集气法,改进测定乙醇分子结构实验的仪器装置,并探索最佳反应条件。另外,设计两个空白实验,结合压强变化曲线对实验误差进行相关讨论。     

光谱仪测试范围的扩展

由于石化行业的生产需要，其材质的使用具有多样性和广泛性，经常会出现顾客委托的测试样品的一个或几个元素跨越光谱仪现有测试程序测量范围的情况。本法通过对光谱仪测试原理的认识，根据光谱仪的测试能力及标样的采集，实现了一个或几个元素测量范围的扩展，并对其测量的影响因素进行了研究。     

Effect of the Method of Modification of Zeolite X on Selectivity of Catalytic Methylation of Toluene

Theoretical and Experimental Chemistry - The effect of the method of modification of catalysts based on zeolite X by cesium and magnesium cations (ion exchange and impregnation) on the selectivity...     

Influence of viscosity of medium on processes of oxygen quenching of excited states of mesoporphyrin

The oxygen quenching rate constants for singlet and triplet excited states of the dimethyl ester of mesoporphyrin IX increase with decreasing viscosity of the medium and reach a maximum at a viscosity of approximately 0.4 mPa·sec, after which the rate constants begin to decrease. The drop in rate constant with increasing fluidity of the medium may be related to a nonequilibrium character of the elementary act in the interaction of the reactants in the solvent cage. In viscous media such as isopropyl alcohol, isobutyl alcohol, and isoamyl alcohol, the reaction radius is greater than the sum of the radii of the reacting particles. The long-range character of these processes is due to the relatively weak dependence of the quenching probability on distance.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 161–167, March–April, 1989.     

Dichroism of absorption and polarization of phosphorescence of molecules of the closed form of nitrobenzospirothiopyran

The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997.     

Synthesis of tetrabenzoporphins of the basis of isoindoline

Chemistry of Heterocyclic Compounds -