共查询到19条相似文献,搜索用时 109 毫秒
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利用手持技术仪器探究盐酸(HCl)和醋酸(HAc)两种不同强度的酸在相同条件下的pH和电导率,把抽象思维转化为直观数据,通过直观数据鲜明地比较它们之间的区别,从而更进一步让学生清楚地比较强酸和弱酸电离时pH和电导率的差别,认识溶液的导电性强弱与溶液中总离子数的多少有密切的联系,以及弱酸溶液是无法完全电离的这一理论知识。 相似文献
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自2010年广东高考改革,把化学科归入理综范畴内,盐类的水解成为高考的热点,从高考命题趋势来看,书写水解方程式,溶液中离子(或溶质粒子)浓度大小比较,仍是2015年高考试题的主流。 相似文献
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示波极谱滴定法测定生物碱盐酸盐类药物 总被引:2,自引:0,他引:2
本文采用交流示波极谱滴定法测定盐酸异丙嗪、盐酸吗啉双胍、盐酸山莨菪碱和盐酸黄连素四种生物碱盐酸盐类药物的含量。该法到目前为止未见报道,它具有快速准确,终点直观的特点,溶液的颜色,产生的沉淀,制剂中的赋形剂对滴定均无影响,可省略分离步骤,简化测定程序。 相似文献
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电解质溶液知识历来是广东高考化学的教学重点,也是高考的重点。其涉及的主要考点有:电解质溶液导电性的比较;强电解质和弱电解质的概念,水的电离和弱电解质的电离平衡;pH的概念及计算;盐类水解的原理;离子浓度大小的比较等。对于这些经久不衰的常考点,我们要格外重视,掌握其解题要领。 相似文献
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利用文蛤壳制备复合氨基酸螯合钙 总被引:3,自引:0,他引:3
初步研究利用文蛤壳酸解制得钙盐,与鸡羽毛酶解成的复合氨基酸结合制备复合氨基酸螯合钙的工艺。重点探讨文蛤壳酸解酸的选择及温度的确定,鸡羽毛的酶解工艺和复合氨基酸螯合钙的螯合条件。结果表明:文蛤壳利用盐酸的效果比较好,酸解温度为110℃;鸡羽毛的最佳酶解条件为:8%木瓜酶,固液比为1:22,pH值9.5,酶解时间16小时;氨基酸钙螯合反应的最佳条件为:反应温度50℃。反应时间30rain,pH=5.0,氨基酸与钙盐的配体摩尔比为3:1。本研究废物被充分利用,工艺简单可行。 相似文献
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主要研究了将重氮盐合成的传统釜式反应器改为管式反应器和重氮盐合成、水解的间歇式反应工艺改为连续的反应工艺,考察了亚硝酸钠和硫酸的用量、亚硝酸钠溶液、硫酸铵盐溶液、尿素的进料速率对间甲酚得率的影响,得出较佳工艺条件为:重氮化温度维持在0~5℃,亚硝酸钠溶液和硫酸溶液的浓度分别为35%和30%,亚硝酸钠与硫酸与间甲苯胺的物质的量比为1.02∶3.6∶1;亚硝酸钠溶液、硫酸铵盐溶液、尿素的进料速率分别为20 mL/min、120 mL/min、0.100 g/min。所得的重氮盐以130 mL/min滴加到水解反应釜,在110~120℃进行水解反应制备间甲酚,间甲酚得率为86.5%,纯度为99.5%。 相似文献
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The compressive strength of dried sand spheres held together by NaCl crystal bridges was investigated. Agglomerate diameter, sand particle size, drying temperature and salt concentration were varied. Compressive strength L was correlated with pellet diameter D by the equation: L=kDn The values obtained forthe parameters k and n were interpreted in terms of the mode of crystallization of the salt and the distribution of the salt bridges. A simple model is presented to explain the variation of the exponent n with the uniformity of binding in agglomerates. 相似文献
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Agne Sveistyte Teresa Gibbins Kimberly J. Tyrrell Carson J. Miller Dr. Matt H. Foley Andrew E. Plymale Dr. Aaron T. Wright Dr. Kristoffer R. Brandvold 《Chembiochem : a European journal of chemical biology》2020,21(24):3539-3543
Animals produce bile to act as an antibacterial agent and to maximize the absorption of lipophilic nutrients in the gut. The physical properties of bile are largely dictated by amphipathic bile salt molecules, which also participate in signaling pathways by modulating physiological processes upon binding host receptors. Upon excretion of bile salts from the gall bladder into the intestine, the gut microbiota can create metabolites with modified signaling capabilities. The category and magnitude of bile salt metabolism can have positive or negative effects on the host. A key modification is bile salt hydrolysis, which is a prerequisite for all additional microbial transformations. We have synthesized five different fluorogenic bile salts for simple and continuous reporting of hydrolysis in both murine and human fecal samples. Our data demonstrate that most gut microbiomes have the highest capacity for hydrolysis of host-produced primary bile salts, but some microbially modified secondary bile salts also display significant turnover. 相似文献
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Zhilong Wang Yajing Guo Da Bao Hanshi Qi 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2006,81(4):560-565
The enzymatic hydrolysis of potassium salt of penicillin G (Pen G) into phenylacetic acid (PAA) and potassium salt of 6‐aminopenicillanic acid (APA) is inhibited not only by the substrate and the product APA but also by the by‐product PAA. The partitioning behaviour of PAA in a cloud point system, a novel two‐phase partitioning system, was determined. Direct extraction of PAA in the process of immobilised penicillin acylase hydrolysis of Pen G without pH control was achieved. Pen G was hydrolysed almost completely and the product APA concentration in the cloud point system was much higher than in the control, suggesting that the cloud point system may be applied as a novel extractive bioreactor for the enzymatic hydrolysis of Pen G. Copyright © 2006 Society of Chemical Industry 相似文献