双指示剂法测定混合碱样的含量

使用双指示剂测定混合碱含量,是根据两个终点消耗的盐酸的体积计算混合碱中的组分与含量,利用溶液化学计量点时颜色的明显变化,判断其滴定终点,整个操作经济实用,步骤简单快捷,测定结果较准确,使用较广泛。     

混合碱测定的三种教法

混合碱的测定是技工学校化工分析(即定量分析)专业课滴定分析法教材中具有一定难度、并具有代表性的一课。其特点是前后衔接紧密,有理论知识,又有实验操作,为综合课型。 其教学目的:使学生理解混合碱(NaOH—Na_2CO_3)的测定原理;掌握“双指示剂滴定”方法。 教学重点:“双指示剂测定”原理 教学难点:两个化学计量点的理解及应用 根据教材特点及教学情境,可采用多种教学方法。 一、讲授法     

自动电位滴定法用于混合碱的测定

在混合碱的测定中,采用自动电位滴定一阶导数曲线法确定滴定终点,与双指示剂法相比,本法具有终点灵敏、误差小等优点,大大提高了测定结果的准确度和精密度.同时也提高了检测的自动化程度,在生产实际中有应用价值。     

双指示剂法测定混合碱误差的主要原因

双指示剂法测定混合碱是一种常用的方法,测定方法简单、实用.但是该方法最大的缺点是测定误差较大.滴定终点判断不准是造成误差的主要原因.     

双指示剂法测定混合碱过程产生偏差的原因及减小的方法

混合碱的测定是分析化学定量实验中最基本的实验之一,是用HCI标准溶液滴定NaOH与Na_2CO_a或NaHCO_3与Na_2CO_3的混合物,实验教材中大都采用双指示剂法(酚酞、甲基橙)来测定混合碱的含量.这种方法简便、快速、实用,但存在着较大的偏差.从整个实验过程进行分析,产生偏差的主要原因有:     

碳酸钠的制备与含量测定实验的改进

以"侯氏制碱法"为原理,用碳酸氢铵和氯化钠制备了碳酸钠,并测定其含量,以传统方法为基础,对碳酸钠的制备和含量的测定步骤做了进一步的改进。探索了制备碳酸钠的条件和产率,比较了双指示剂法和电位滴定法等测定碳酸钠含量的方法。通过无机化学和分析化学实验中碳酸钠的制备与含量的测定实验,促进了学生实验技能的培养。     

天然水中碳酸测定有关问题的探讨

介绍了天然水体中碳酸的来源、存在形式及平衡关系；指出用“双指示剂”法测定水中碱度的第一终点应显粉紫色，第二终点宜采用甲基红一溴甲酚绿混合指示剂；测定游离二氧化碳要用双样测定并严格控制滴定终点；各种碳酸的含量可与pH值、硬度的测定结果进行校核。     

植物靛蓝在水碱度分析中的指示作用

利用植物靛蓝与甲基橙组成的混合指示剂测定水的碱度,并与其它种类指示剂测定水碱度的效果进行对比实验研究.结果表明:甲基橙-靛蓝混合指示剂性质稳定,滴定终点变色敏锐,易于操作,可有效地提高测定结果的准确度,是测定水碱度较为理想的指示剂.     

测定水泥中氧化镁含量时K—B指示剂的影响

采用《水泥化学分析方法》（GB／T176-2008）测定水泥中氧化镁时,酸性铬蓝K-酚绿B混合指示剂（K—B混合指示剂）是影响测定结果的重要影响因素之一,通过大量实验比较,发现当K-B混合指示剂的比例为1：1．2,加入量为0．1g时,滴定终点明显。     

双指示剂法测定混合碱实验条件的优化

本文分析了双指示剂法测定两类混合碱的机理,指出影响测定结果准确度和重现性差的原因,并介绍了作为分析实验的优化条件。     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

胡主席在印度,我却在中国

Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer.     

STORIES

正A One day a pig went to the stable(马棚)to see his good friend,an oldhorse,and was going to stay there forthenight.Night came and it was time forsleep.The pig went into the straw heap(稻草堆)and lay comfortably.A longtime passed,but the horse was stillstanding there and did not move.Thepig asked the horse why he did not go tosleep."Standing like this is the begin-ning ofsleeping,"answered the horse.     

巧妙引语(英文)

正1.Any fool can count the seeds in an apple.Only God can count all the apples in one seed.2.Happy families are all alike;every unhappy family is unhappy in its own way.3.Memories are the key not to the past,but to the future.4.Sometimes in the dark you see what you want to see.5.There is a great difference between     

Information for Authors

正Scope and Policy The Journal of Chongqing University-English Edition(JCQU-E)is a peerreviewed journal publishing research articles in multiple disciplines of science and technology,covering civil and environmental engineering,chemical engineering,biotechnology,mechanical and electrical engineering,computer and data processing,mining,metallurgy,materials science,and interdisciplines thereof.