氯化钠提纯实验中几个重要问题的讨论

氯化钠提纯实验是高校化学类各专业的典型实验,涉及基础化学实验中的称量、溶解、沉淀、pH值测定、常压过滤、减压过滤、蒸发浓缩、结晶干燥、离子定性鉴定等基本操作。本文讨论了氯化钠提纯实验中影响纯度的几个重要问题,分析了难溶盐BaSO₄、BaCO₃应该分步过滤除去的理论依据。研究表明,溶液酸度控制在pH=2～3可以完全除去溶液中的过量Na₂CO₃;溶液中少量K⁺在蒸发浓缩、减压过滤时除去。通过上述步骤,可以得到纯度级别非常高的精盐。     

苯甲酸制备实验回收二氧化锰及含量测定

在有机化学实验苯甲酸的制备实验中,用甲苯作原料,用高锰酸钾作氧化剂,把苯甲酸氧化成苯甲酸钾,加入的高锰酸钾是过量的,需要用亚硫酸钠除去,减压过滤,得到苯甲酸钾溶液,再用盐酸酸化,制得白色苯甲酸固体.减压过滤后的滤渣是高锰酸钾和亚硫酸钠反应后生成的碱式氧化锰,煅烧碱式氧化锰可制得二氧化锰.用氧化还原滴定测得二氧化锰含量....     

葡萄籽中花色素的分离研究

以葡萄籽为原料 ,甲醇做提取剂 ,冷浸 12h ,70℃回流提取 3次 ,每次 2h ,合并提取液 ,减压浓缩至浸膏状 ,热水溶解 ,趁热过滤除杂 ,滤液用正丁醇萃取 2次 ,萃取部分经减压浓缩 ,真空干燥 ,得花色素产品 ,经测定 ,花色素的质量分数可达 90 %以上     

磷钼酸喹啉容量法改进点滴

<正> 现在国内外测定磷矿石、过磷酸钙及其它磷酸盐中P_2O_5含量大多采用容量法。该法过滤洗涤沉淀至中性很费时时。为了加快过滤洗涤沉淀的速度,日本用古氏坩埚、玻璃纤维滤纸、减压洗涤过滤。因为磷钼酸喹啉在中性和酸性中稳定,笔者在日本方法的基础上,采用双     

关于过滤技术改进的几点意见

目前化工生产过程中最成问题的是“后处理”操作。这些操作主要包括过滤和干燥等方面。近年来虽不断有所改进,但是发展还不够快。有些新技术的推广应用也未受到足够重视。本文拟就过滤操作技术方面的改进,提供一些初步的参考意见。一、目前化工生产中过滤设备的使用情况十八世纪开始,人们采用减压、加压和离心力等作用,强化了过滤过程,络续制备了真空吸滤器、板框压     

介绍一种液面自控实验过滤装置

过滤是化学实验一项基本操作。化学实验室过滤一般使用三角漏斗渗滤或减压抽滤，过滤液量较少时尚能基本满足实验需要，当过滤量较大时，这些装置就很难适应。据悉某大学化学实验室曾经用１ｔ某地软锰矿做提取硫酸锰制电解二氧化锰实验，过滤总液量达几吨，实验室无适用的...     

高压天然气管道内粉尘在线检测方法

针对高压天然气管道分输站场用过滤分离设备性能评价和设备选型的要求,利用小孔节流效应设计了适合高压管道取样用减压装置,在此基础上提出了高压天然气管道内粉尘在线检测方法。采用数值计算与现场试验相结合的方法,验证了粉尘在线检测方法,结果表明减压装置减压过程中无液滴析出、对粉尘浓度和粒度分布影响小,在线检测方法检测结果准确可靠。     

从大豆油渣中提取大豆多糖的研究

1份大豆油渣和12份10％～13％的碱溶液(重量比)混合,在50℃提取45min,减压过滤,滤液保存备用。滤渣用10％的次氯酸钠溶液脱色,用热水、乙醇等顺序洗涤,过滤,干燥,粉碎过筛,得到淡米黄色的粉状产物——大豆多糖,得率28.73％。     

甲基嘧啶磷的绿色合成研究

以嘧啶醇和碳酸钾水溶液在有机溶剂中反应减压脱水,生成嘧啶醇钾盐与甲基氯化物进行缩合反应,经过滤、减压浓缩得到甲基嘧啶磷。优化的反应条件为：以甲苯为溶剂,n（嘧啶醇）∶n（碳酸钾）=1.0∶2.0,嘧啶醇钾盐含水量<0.1%,反应温度30～40℃,反应时间6 h。优化条件下,甲基嘧啶磷纯度98.5%,收率92.6%,该工艺转化率高、收率高、三废少,符合绿色环保生产理念,具有工业化应用前景。     

列管式真空蒸发器的快速取样装置

<正> 浓缩工序是明胶生产中的一个重要工序,其主要作用是利用减压蒸发器将水分从过滤后的稀明胶溶液中蒸发除去,提高明胶溶液的浓度,为明胶冷冻干燥创造有利条件,缩短干燥过程中的时间,达到节     

HPLC法测定肉制品中苯甲酸、山梨酸、脱氢乙酸

建立用高效液相色谱二极管阵列检测器测定肉制品中苯甲酸、山梨酸、脱氢乙酸的方法。肉制品中苯甲酸、山梨酸、脱氢乙酸经水蒸气蒸馏,用高效液相色谱二极管阵列检测器测定,外标峰面积法定量。苯甲酸、山梨酸、脱氢乙酸在2~100 mg/kg范围内呈良好的线性关系,3个水平(2.0、20.0、80.0 mg/kg)添加苯甲酸、山梨酸、脱氢乙酸的回收率为84.3%~91.1%,相对标准偏差(RSD)为1.04%~2.06%,检出限为2.0mg/kg。此方法具有简单、快速、准确等优点,适用于脂肪含量较高的肉制品中苯甲酸、山梨酸、脱氢乙酸的测定。     

Preparation, Characterization and Adsorption Performance of Cetyl Pyridine Bromide Modified Bentonites

Benzoic acid removal is important for the water treatment and adsorption is an effective treatment process. Cetyl pyridine bromide-modified bentonites (CPB-Bent) and hydroxy-aluminum-pillared bentonites (Al(OH)-Bent) were prepared and characterized by XRD, FTIR and BET. Adsorption experiments were conducted on the adsorption of benzoic acid onto natural bentonites, sodium bentonites (Na-Bent), Al(OH)-Bent and CPB-Bent in batch experiments. Benzoic acid removal onto CPB-Bent is pH dependent and the optimum adsorption is observed at pH ~3.5. The adsorption rate was fast and equilibrium was established within 90-min. The adsorption rate of benzoic acid on CPB-Bent fit a pseudo-second order kinetics model well (R ² = 0.999). The results were analyzed according to the Henry, Langmuir, Freundlich, and Dubinin-Radushkevich isotherm model equations. The adsorption data is well interpreted by the Langmuir isotherm model. Benzoic acid solution at a concentration of 0.5 mmol/L was adsorbed by CPB-Bent; and, the final adsorption efficiency was greater than 90%. The results show that benzoic acid adsorption capability of CPB-Bent is high with the maximum adsorption capability of 94.34 mg/g, which suggests that CPB-Bent is an excellent adsorbent for effective benzoic acid removal from water.     

RP-HPLC测定糕点中多种添加剂含量的研究

苯甲酸(钠)、山梨酸(钾)、脱氢乙酸作为防腐剂,安赛蜜、糖精钠作为甜味剂,被广泛应用于各种糕点生产中,但是,使用过量会对人体健康造成伤害。我们利用高效液相色谱法对糕点中的安塞蜜、苯甲酸、山梨酸、糖精钠、脱氢乙酸五种添加剂进行同时测定,分离效果好,分离时间短,此方法操作简便、快速可靠、便于推广。     

催化加氢法合成苯甲醛研究进展

综述了国内外苯甲酸及其酯催化加氢制备苯甲醛技术的研究进展,并针对当前研究状况,提出了改进办法以及新型苯甲醛生产综合途径。     

苯甲酸釜残液全部回收的工艺开发利用

Benzoic acid residue is solid waste produced from the production of benzoic acid by oxidizing toluene. Because it contained important chemical raw materials such as benzoic acid, benzyl benzoate and fluorenone, it is necessary to recover them from the residue. In this work the technique featured with high efficiency evaporation and vacuum distillation was developed to obtain total recovery and utilization of the benzoic acid residue. By controlling the operation temperature at 260°C and the pressure of 16 kPa in the rising and falling film evaporators, heavy components separated efficiently from the residue can be polymerized and the light components consisting of 63% of the residue entered into a benzoic acid vacuum distillation column. Keeping the temperature of polymerization at (280±10)°C, coumarone resin was produced after adjusting the softening point according to the market re-quirements. Vacuum distillation was operated under the following conditions: top temperature at 186°C, top pres-sure of 16 kPa, bottom temperature at 240-250°C, reflux ratio being 3︰1. Benzoic acid of 98% purity was distilled out from the column as a side stream and the bottom product was crude benzyl benzoate. By the developed tech-nique, the benzoic acid residue was splitted into three products, benzoic acid, crude benzyl benzoate and coumarone resin without any surplus waste.     

槽外法苯甲酸催化甲苯电合成苯甲醛

以苯甲酸作相转移催化剂,Mn3+/Mn2+为媒介,甲苯为原料,采用槽外法电合成苯甲醛。利用正交实验研究了H2SO4浓度、反应温度和苯甲酸用量对苯甲醛生成速率和产率的影响。结果表明,当每升甲苯含8 g苯甲酸、水相H2SO4浓度为51.6%和反应温度85℃时,苯甲醛的收率大于93%。     

苯甲醛氧化制备苯甲酸的研究

以氧气为氧化剂,在六水合氯化钴催化剂作用下,催化氧化苯甲醛制备苯甲酸,分别考察了温度、溶剂量、催化剂量、乳化剂量对苯甲酸收率的影响.在苯甲醛:水:乳化剂:六水合氯化钴质量比为75:50:37.5:0.075,反应温度75～80℃,反应时间6 h,氯气流量0.3 L/min下反应,产率在85%以上,用水进行两次重结晶,得率为60%～65%.     

Catalytic and noncatalytic esterification and transesterification by subcritical methanol

The model reactions of benzoic acid (BA) esterification and ethyl benzoate (EB) transesterification by subcritical methanol were carried out for the first time at 220° C without catalysts in order to decrease the acid wastes from an industrially important reaction of the synthesis of biodiesel components. Methanol under these conditions is both a solvent and a catalyst. Benzoic acid is esterified in quantity even when the ratio of BA to methanol is 1: 3. Benzoic acid transesterification occurs with 82% conversion and a BA-to-methanol ratio of 1: 10. A process is proposed for biodiesel manufacturing from vegetable oil under the specified conditions and in the presence of a solid acid catalyst (sulfated TiO₂, SnO₂, or Al₂O₃). With the use of sulfated TiO₂, biodiesel fuel yields can reach 98% at 170 °C. Our results can be used in the large-scale production of biodiesel fuel components because they show a way to seriously decrease costs for recycling acid emissions and the load on the environment.     

高效液相色谱法同时测定饮料中苯甲酸、山梨酸和糖精钠

采用高效液相色谱法同时测定饮料中苯甲酸、山梨酸和糖精钠,外标法定量。苯甲酸、山梨酸和糖精钠检测限分别为0．063μg／mL、0．048μg／mL和0．051μg／mL,变异系数分别为1．34％、1．29％和1．11％,回收率分别为98．69％、98．34％和98．98％。     

Allelopathic effects ofPinus densiflora on undergrowth of red pine forest

Correlation between the distributional frequency of undergrowth species of red pine forest and their germination and growth effected by pine extracts and leachates was found. It was made clear by germination and growth tests that pine toxic substances inhibit the germination and growth of low frequency species more than high frequency species in a red pine forest and that these substances are contained in descending concentration in fresh and fallen leaves, roots, pine forest soil, and pine rain. The concentration of pine toxic substances in extracts or leachates was affected by extracting or leaching within a given period of time, requiring a few hours for extracts or a few days for leachates. The amount of dry weight inhibition of the undergrowth treated by pine leachates was expressed as a growth inhibition index (GII) for the comparison of tolerance in various species. GII is a relative value (%) of the test groups against the control and it is an exponential function of the amount of pine toxic substances affecting the dry weight of the undergrowth. The substances were analyzed by paper and gas chromatography. Benzoic acid and 11 phenolic acids were identifed by gas chromatography. Benzoic acid was considered to be a key factor of allelopathy in the red pine forest.