小型简易电石爐生产电石的几个问题的商讨

小型簡易电石炉是指电石炉容量在1000千伏特安培以下,不需要冷却设备者。这种电石炉的特点是:构造簡单,操作容易,占地少,用料少,投資少,时間快,易于推广。现将我們搞小型简易电石炉生产电石初步获得的几点体会介绍如下: 一、电石生产的基本原理及工艺流程电石是把石灰和碳素原料(焦炭或无烟煤)放在电炉内熔融制成的,其反应如下: CaO 3C(?)CaC_2 CO—108,000千卡 (1) 根据(1)式,可知电石的生成反应,是一个吸收大量热的反应,也就是說,电石需在高温下才能生成。生成的温度是在1,800—2,200℃之间,現在都是利用电     

电石泥渣分析

研究建立了电石泥渣的分析方法，并对试样进行了系统分析，105～110℃干燥重量法测自由水；用差热分析确定试样中氢氧化钙的实际分解温度，在580～600℃灼烧重量法测化合水，动物胶凝聚的二氧化硅沉淀中，先用重量法测出二氧化硅和碳渣含量，再用氢氟酸挥发除去其中的二氧化硅，再恒重，测出残渣即为碳渣含量，通过差减法测出二氧化硅含量；滤液中用磺基水杨酸分光光度法测三氧化二铁，铬天青S光度法测三氧化二铝，变色酸光度法测二氧化钛，EDTA容量法测氧化钙，EGTA容量法测氧化镁。通过分析，对电石泥渣各组分的存在形式作了正确判断。经误差分析，证明方法准确可靠，切实可行。     

绿色荧光蛋白质(GFP)的发现、表达和发展

本文简要地介绍了2008年Nobel化学奖——绿色荧光蛋白质的主要学术内容,包括绿色荧光蛋白质的发现、发展和工作的重要意义.类-绿色荧光蛋白质可用于在时间和空间上监视越来越多的活细胞中的现象和机制,如基因表达、蛋白质的定位和动态学等.因此可以说,绿色荧光蛋白质的发现是联系到生物科学上的一次技术革命.     

硅元素的发现及其概念的发展

通过对硅元素发现历程的考证分析可知,17、18世纪随着科学实验的兴起以及元素观的发展,科学家以实践为基础,运用逻辑思维和直觉思维预见了硅元素的存在;19世纪随着电化学和分析化学的发展,科学家们成功制取无定形硅和晶体硅;20世纪30年代,硅同位素的发现使人们对硅元素的概念有了新认识.总之,随着科学思想的演进和科学方法的发...     

维生素K的发现和研究

一项科学研究常开始于一个特殊的问题,当问题得到最终解决时就成为科学发现和发明。但在科学史上人们常发现科学家们并不是都能“种瓜得瓜,种豆得豆”,所做的研究往往会出现一种“种瓜得豆”的现象。这种偶然和意外的发现往往会使人们觉得神秘,许多人将之归因于运气、天才。但如果我们做一番仔细的研究,就会发现其中的必然。维生素K的发现和研究就是偶然中显示必然的一个例子。故事的最初发生在1928年的哥本哈根,丹麦化学家Henrik Dam博士对胆固醇感兴趣,想要研究如果动物所吃的食物中不含胆固醇,它们能不能利用身体内的其他化学物质制造…     

化学元素的发现和名称便览

化学工作者经常同化学元素打交道,应该知道每个化学元素是谁发现的?怎么发现的?什么时候发现的?当时为什么给它起这么个名字?初学化学的人更想了解它。虽然在无机化学参考书中都能查到,然而没有象化学元素周期表那样查阅方便,缺乏完整、系统、简明的资料。笔者从达个愿望出发,按原子序数为序整理成表格,以期给从事化学教学工作和初学者提供一点方便,也可以从发现元素的史实中得到启发,对今后从事化学工作有所裨益。     

瑞利和氩元素的发现

约翰·威廉·斯特拉特,瑞利男爵三世(John William Strutt,Third Baron Rayleigh)于1842年11月12日生于英国埃塞克斯郡莫尔登的朗弗尔格罗甫。他的父亲是第二世男爵,母亲是海军上校的小女儿。     

抗疟疾药物的发现与发展

疟疾伴随着人类历史存在,威胁着人类健康,特别是在非洲地区尤为严重,抗疟疾药物的研究成为药物化学史上光辉的一页。从最初的金鸡纳药物着手,逐步介绍奎宁、喹啉类、嘧啶类、青蒿素及其衍生物等抗疟药物在抗疟史上的发现、合成及推广,同时介绍了几类药物的作用机理。     

钛元素的发现及其概念发展

1791年,英国矿物学家格雷戈尔发现钛矿石并意识到一种新元素的存在。至1795年,普鲁士化学家克拉普罗特进一步预言了该元素,并将之正式命名为钛(Titanium)。1910,美国化学家亨特制取了纯净的钛单质,钛元素的概念正式形成。20世纪20年代以后,钛同位素的发现使人们对钛元素概念有了新认识,并逐渐形成现代钛元素概念。钛元素概念的发展使人们在科学认知上发生了转变,促进了化学元素观的演进。     

钨元素的发现及其概念的发展

1781年,瑞典化学家舍勒在白钨矿中发现了钨酸,预测其中一定含有一种新金属元素,并将其命名为钨(Tungsten)。1783年,西班牙化学家德鲁亚尔兄弟从黑钨矿中成功提取出了舍勒所说的新金属单质,将其命名为钨(Wolfram)。1803年,英国化学家道尔顿原子论的提出,赋予钨元素新的含义:具有一定质量的钨原子。1930年以后,钨同位素的发现使人们对钨元素有了新认识,并逐渐形成了现代钨元素的概念。关于钨元素的认识经历了从假说到客观存在、从定性到定量、从宏观到微观的发展历程。钨元素概念的演变体现了科学思想和科学方法的进步。     

Solid-Phase Synthesis of Calcium Carbide in a Plasma Reactor

A laboratory-scale spout-fluid bed reactor with a dc plasma torch was used to study the solid-phase synthesis of calcium carbide. Calcium oxide powder with a mean particle size of 170 m was reacted with graphite powder (130 m). Argon was used to initiate the plasma and hydrogen gas was then added to increase power and raise the plasma jet enthalpy. Experimental results showed that the reaction took place in the vicinity of the plasma jet and that conversion to calcium carbide increased linearly with reaction time. The rate of conversion increased exponentially with plasma jet temperature, indicating that chemical reaction was the controlling mechanism. Microscopic analysis of the solid product showed that calcium carbide was formed around both reactants, and that the reaction followed a shrinking core model. Although melting and agglomeration of partially reacted particles occurred at high temperature, resulting in instability of the bed and impeding the reaction progress, high conversions are expected in a continuous process with optimized reactor design.     

直接以碳化钙为炔源合成有机化合物

以往利用碳化钙作为原料制备有机化学品时, 首先须将碳化钙转化成乙炔气体, 再由乙炔气体进一步制备有机化合物, 而乙炔气体易燃易爆, 反应条件苛刻, 应用受到一定限制。碳化钙可以由可再生的生物炭在较低的温度下快速制备, 是一种绿色经济的化工原料。因此, 直接利用碳化钙作为绿色炔源代替乙炔气体、乙炔试剂制备各种重要有机化学品将是一条简洁的绿色化学途径。本文综述了直接以碳化钙为炔源合成有机化合物的反应类型、反应机理以及研究现状, 展望了碳化钙作为固体炔源构建有机化合物的发展趋势。     

Calcium Carbide: A Unique Reagent for Organic Synthesis and Nanotechnology

Acetylene, HC≡CH, is one of the primary building blocks in synthetic organic and industrial chemistry. Several highly valuable processes have been developed based on this simplest alkyne and the development of acetylene chemistry has had a paramount impact on chemical science over the last few decades. However, in spite of numerous useful possible reactions, the application of gaseous acetylene in everyday research practice is rather limited. Moreover, the practical implementation of high‐pressure acetylene chemistry can be very challenging, owing to the risk of explosion and the requirement for complex equipment; special safety precautions need to be taken to store and handle acetylene under high pressure, which limit its routine use in a standard laboratory setup. Amazingly, recent studies have revealed that calcium carbide, CaC₂, can be used as an easy‐to‐handle and efficient source of acetylene for in situ chemical transformations. Thus, calcium carbide is a stable and inexpensive acetylene precursor that is available on the ton scale and it can be handled with standard laboratory equipment. The application of calcium carbide in organic synthesis will bring a new dimension to the powerful acetylene chemistry.     

Modern Approaches in the Discovery and Development of Plant-Based Natural Products and Their Analogues as Potential Therapeutic Agents

Natural products represents an important source of new lead compounds in drug discovery research. Several drugs currently used as therapeutic agents have been developed from natural sources; plant sources are specifically important. In the past few decades, pharmaceutical companies demonstrated insignificant attention towards natural product drug discovery, mainly due to its intrinsic complexity. Recently, technological advancements greatly helped to address the challenges and resulted in the revived scientific interest in drug discovery from natural sources. This review provides a comprehensive overview of various approaches used in the selection, authentication, extraction/isolation, biological screening, and analogue development through the application of modern drug-development principles of plant-based natural products. Main focus is given to the bioactivity-guided fractionation approach along with associated challenges and major advancements. A brief outline of historical development in natural product drug discovery and a snapshot of the prominent natural drugs developed in the last few decades are also presented. The researcher’s opinions indicated that an integrated interdisciplinary approach utilizing technological advances is necessary for the successful development of natural products. These involve the application of efficient selection method, well-designed extraction/isolation procedure, advanced structure elucidation techniques, and bioassays with a high-throughput capacity to establish druggability and patentability of phyto-compounds. A number of modern approaches including molecular modeling, virtual screening, natural product library, and database mining are being used for improving natural product drug discovery research. Renewed scientific interest and recent research trends in natural product drug discovery clearly indicated that natural products will play important role in the future development of new therapeutic drugs and it is also anticipated that efficient application of new approaches will further improve the drug discovery campaign.     

利用电石渣制备轻质碳酸钙浸渍液中主组分的测定

对用电石渣制备轻质碳酸钙工艺过程的浸渍液中钙(Ⅱ)、氯离子、游离氨和铵离子的测定方法进行系统试验。提出了煮沸蒸发使游离氨直接被硫酸溶液吸收,然后用碱滴定法间接测得游离氨的含量;氯离子采用硝酸根标准溶液沉淀滴定法;铵离子采用在碱溶液中使铵根离子转化氨气蒸馏逸出,用硫酸溶液吸收后氢氧化钠标准溶液滴定的方法;钙(Ⅱ)采用EDTA滴定法。方法的相对标准偏差(n=5)在1.4%~2.4%之间。     

Transesterification of Soybean Oil Catalyzed by Calcium Hydroxide which Obtained from Hydrolysis Reaction of Calcium Carbide

Calcium carbide residue (CCR) was investigated in transesterification reaction of triglycerides to determine its viability as a solid catalyst for biodiesel synthesis. Literature survey showed that CCR has never been studied as a solid catalyst in the transesterification of triglyceride. The scope of the study includes the effects of CCR calcination temperature, calcination time, the alcohol/oil molar ratio, the catalyst amount (wt % of oil) and the reaction time. The relationship between chemical composition and catalytic activity of waste cement was also investigated. These CCR catalysts, thermally activated at 600 °C, can give rise to fatty acid methyl esters (FAME) purity higher than 99.5%, after 3 h of reaction, when oil/methanol molar ratio of 1/12 and 1 wt % of the catalyst were employed. Application of CCR as catalyst for biodiesel production in this study may not only provide a cost‐effective and environment friendly way of recycling CCR waste but also reduce hopefully the cost of biodiesel production.     

Experimental Investigation on the Mass Diffusion Behaviors of Calcium Oxide and Carbon in the Solid-State Synthesis of Calcium Carbide by Microwave Heating

Microwave (MW) heating was proven to efficiently solid-synthesize calcium carbide at 1750 °C, which was about 400 °C lower than electric heating. This study focused on the investigation of the diffusion behaviors of graphite and calcium oxide during the solid-state synthesis of calcium carbide by microwave heating and compared them with these heated by the conventional method. The phase compositions and morphologies of CaO and C pellets before and after heating were carefully characterized by inductively coupled plasma spectrograph (ICP), thermo gravimetric (TG) analyses, X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The experimental results showed that in both thermal fields, Ca and C inter-diffused at a lower temperature, but at a higher temperature, the formed calcium carbide crystals would have a negative effect on Ca diffusion to carbon. The significant enhancement of MW heating on carbon diffusion, thus on the more efficient synthesis of calcium carbide, manifested that MW heating would be a promising way for calcium carbide production, and that a sufficient enough carbon material, instead of CaO, was beneficial for calcium carbide formation in MW reactors.