EDTA滴定法测定再生锌原料中的锌含量

采用氟化铵-盐酸-硝酸-硫酸分解样品,氨水沉淀分离铁、锰、铅等共存元素,滤液中加入掩蔽剂掩蔽少量干扰元素,在pH=5～6的乙酸-乙酸钠缓冲溶液中,以二甲酚橙为指示剂,用EDTA标准滴定溶液滴定。测得结果为锌、镉合量,扣除镉量,即为锌量。方法用于测定再生锌原料中锌,结果的相对标准偏差(RSD,n=11)为0.15%～1.0%。按照实验方法对再生锌原料样品进行加标回收实验,回收率为99.1%～102%。能满足日常对再生锌原料中锌含量的检测要求。     

EDTA滴定法测定分银渣中的铅含量

采用氟化铵-盐酸-硝酸-高氯酸溶解样品,加入氢溴酸除去样品中的砷、锑、锡等共存元素,加入硫酸将样品中的铅转化为硫酸铅沉淀,通过过滤与其它元素分离,滴定前加入巯基乙酸掩蔽铋,在乙酸-乙酸钠缓冲体系下,以二甲酚橙为指示剂,建立了采用EDTA络合滴定法测定分银渣中铅含量的方法。实验方法用于测定分银渣中的铅含量,测定结果的相对标准偏差(RSD,n=11)为0.32%～0.90%,加标回收率为100%～102%。能够满足日常测定需求。     

EDTA滴定法测定含锌物料中氧化锌

采用氯化铵-氨水体系溶解试样,干过滤后,向移取的滤液中加入氯化钡和硫酸共沉淀铅离子,过滤分离硫酸铅沉淀,向滤液中加人抗坏血酸、氟化钾、硫代硫酸钠等掩蔽剂掩蔽少量干扰元素。在pH=5~6的乙酸-乙酸钠缓冲溶液中,以二甲酚橙为指示剂,用EDTA标准滴定溶液滴定测得结果为氧化锌、水溶性锌和镉合量,扣除由原子吸收光谱法测得的水溶性锌量和镉量,即为氧化锌量。对总氨浓度、氯化铵-氨水浓度比、溶液加入量、搅拌时间、共存离子干扰、精密度等进行了实验,建立了EDTA滴定法测定含锌物料中氧化锌物相的分析方法。实验证明,氧化锌含量在24%~83%时,方法精密度(RSD)为0.25%~0.54%,加标回收率在99%~104%,完全满足含锌物料中氧化锌的测定要求。     

含钡铅矿石中铅测定的EDTA容量法分析

以硫酸为介质沉淀铅,形成硫酸铅沉淀,过滤除去溶液中的其他干扰元素,用PH介于5-6之间的乙酸-乙酸钠为缓冲液将硫酸铅沉淀溶解,采用二甲酚橙为指示剂,采用EDTA容量法测定含钡铅矿石中铅含量。通过试验证明,EDTA容量法有效的克服了国家标准法测定流程复杂、流程长、溶矿复杂等缺点,通过验证,试验结果和标准值相差不大,该方法的精密度RSD%在0.1%-0.8%之间,方法快速、简便,分析结果符合相关的质量标准。     

沉淀分离-EDTA返滴定法测定卡尔多炉渣中的铅量

采用沉淀分离-EDTA返滴定法建立了卡尔多炉渣中铅含量的测定方法,探讨了样品中共存元素干扰及操作细节等因素对分析结果的影响。实验表明,氟化氢铵用量0.10g、硫酸洗涤次数5～6次、陈化时间3h、氨水加入量5mL、乙酸乙酸钠缓冲溶液加入量30mL、微沸时间15～20min时,方法的加标回收率99.8%～100%,两个实际样品测定结果的相对标准偏差(RSD,n=8,分别为0.14%和0.15%。方法准确度高,精密度好。     

EDTA络合滴定法测定选铁尾矿中CaF_2含量

采用EDTA络合滴定法测定选铁尾矿中的氟化钙含量。选用稀乙酸浸取试样中的碳酸钙,分离过滤氟化钙,用锆-二甲酚橙褪色分光光度法测定浸取液中的氟含量,折算为在稀乙酸中微溶的氟化钙的量;同时沉淀部分用氯化铝溶液在沸水浴中溶解浸取氟化钙,以三乙醇胺掩蔽干扰离子,在KOH介质中,以钙指示剂为指示剂,用EDTA标准滴定溶液测定沉淀中氟化钙的量,两者之和为试样中氟化钙的含量。用此法对试样进行11次平行测定,相对标准偏差(RSD)小于1.0%。在选铁尾矿试样中加入萤石标准物质进行加标回收实验,加标回收率在99%~102%。方法流程短,操作简单。精密度和加标回收率均能满足要求。     

EDTA滴定法测定除尘灰中锌含量

采用灰化后再溶解试样的方法,成功解决了除尘灰因碳含量过高而难于溶解的问题;将灰化后的试样以HCl-HNO3-HF-HClO4混酸溶解,在氯酸钾存在下,以铁盐作载体,用氨水沉淀分离大部分铁、铝、铅等元素,以硫脲-氟化物、硫代硫酸钠、抗坏血酸作掩蔽剂,掩蔽剩余少量铜、锡、铁等干扰元素,在pH=5.5~6条件下,以二甲酚橙为指示剂,用EDTA标准溶液滴定得到锌的含量。方法的相对标准偏差在0.75%~2.8%,加标回收率在98.0%~102%。方法操作简便,且分析结果准确度、重现性较好,可以满足生产检验的需要。     

硫酸铁铵滴定法测定钨钛合金中钛的含量

建立了硫酸铁铵滴定法测定钨钛合金中钛含量的新方法。以硝酸-氢氟酸溶解样品,在25mL NaOH(100g/L)的强碱性介质中,以铁为载体,沉淀分离被测定元素钛后,用盐酸溶解沉淀。在酸性条件下,用铝片还原Ti~(4+)至Ti~(3+),以硫氰酸盐为指示剂,用硫酸铁铵标准溶液滴定至红色为终点。根据消耗硫酸铁铵滴定溶液的体积,求得样品中钛含量。按照实验方法测定样品中钛含量,结果的相对标准偏差(RSD,n=11)为0.40%,加标回收率为99.8%~101%。方法有很好的精密度和准确度,可用于钨钛合金中钛含量的分析。     

铸造锌合金中铜的测定-EDTA分光光度法

本文采用醋酸-醋酸钠缓冲溶液控制PH值.用EDTA作显色剂测定锌合金中的铜,同时有利用EDTA掩蔽锌、铝等元素以消除其干扰.Cu+2与EDT生成11蓝色络合物,该络合物溶液的最大吸收波长在730mm处,表观摩尔吸光系数为93.2.铜量在0～15 mg/100ml符合比尔定律.虽然显色反应的灵敏度不高,但通过增加取样量、加大比色皿厚度,仍可用于锌合金中0.x～10%的铜的测定.本法试剂用量少,操作简便、快速,精密度高,结果令人满意.     

富锂固溶体正极材料中锰含量的测定

为了制定富锂固溶体正极材料的生产工艺,需要对其前驱体中锰含量进行准确测定,以硝酸铵为氧化剂,采用磷酸固定锰的价态,用硫酸亚铁铵标准溶液滴定锰的容量法来测定锰含量,并对溶样方法及温度控制、磷酸的加入量、加入硝酸铵时的温度控制和硝酸铵的加入量等条件进行了优化实验,实验结果表明:称样量为0.300 0g,溶样消耗盐酸10mL,加入10mL H3PO4,溶液温度240℃时加入1.2g硝酸铵进行氧化,测定准确度最高,加标回收率为99.70%~100.5%,相对标准偏差小于0.24%,方法耗时短,不需要加入任何掩蔽剂,适合实际分析采用。     

Lead in candle emissions

The candle-using public should be made aware that the core of candle wicks may contain lead. Used as a stiffening agent to keep the wick out of the molten wax, lead can be emitted as particulates to the air and then deposited on indoor surfaces. To define the problem, 100 sets of candles (two or more identical candles) were purchased locally. The criterion for purchase was that the candles must appear to contain a metal-cored wick or be covered by a metallic pigment. Of the candles purchased, 8% contained lead wicks. The wicks were 39-74% lead (the remainder was fabric or paper) and the lead cores (approx. 100% lead) had linear densities of 13-27 mg/cm. Candles were burned to completion in a closed chamber to capture the air emissions, and the candle residue was extracted to assess the lead mass balance. It was found that individual candles emitted lead to the air at average rates that ranged from 100 to 1700 microg/h. Assuming realistic indoor conditions, these emission rates were modeled to project room air concentration, child exposure by inhalation, and indoor deposition. Results showed that burning single candles can easily raise the source room concentration above the ambient air lead concentration limit of 1.5 microg/m3 set by EPA. Burning multiple candles can elevate it above OSHA permissible exposure limits of 50 microg/m3. Although blood lead levels have dropped precipitously in the United States since lead was phased out of gasoline in 1986, nearly 900,000 children still had levels above 10 microg/dl during NHANES III. Considering that candle sales in the US are estimated at $1-2 billion per year, and that children may spend as much as 88% of their time indoors, it is reasonable to suspect that some blood lead elevation in children arises from indoor micro-environments where lead-wick candles are burned.     

Lead contamination of snow

Snow from disposal sites and along roads contained considerable lead due to the combustion of leaded gasolines by automobiles. In spite of lead concentrations up to 4330 ppm in the sample sediment, the highest concentration in the filtrates was 0.21 ppm with the average, 0.04 ppm. Thus, the dumping of snow away from water-courses instead of directly into them significantly reduces lead contamination of the waters from this source.     

Particulate Lead in Water Supplies

This paper describes research in areas where the occasional failure to meet the EC standard for lead in drinking water is due to the presence of particulate lead. A method is described to disinguish between soluble, particulate and colloidal lead in tap water, and characteristics are given of water sources which are most likely to suffer from this form of lead problem. At least two types of particulate (insoluble) lead in tap water have been identified, and some factors are discussed which cause the occurrence of both types. Interim results of trials are presented, with remedial actions.     

Lead levels in Birmingham dust

Dust is important as a factor affecting amenity and there are suggestions that it can make a significant contribution to the exposure of children to toxic materials and particularly to lead. The results are presented of an investigation into the lead concentrations in dust collected in Birmingham. Relationships are shown to exist between samples from similar areas and the distributions of lead concentrations throughout the City are shown. However, interpretations must be made with caution and this is illustrated by referring to some of the problems involved in the collection and chemical analysis of the samples.     

某高铅暴露区儿童齿铅水平及其健康影响

目的探讨高铅暴露对儿童齿铅水平及其健康影响。方法分别选取高铅暴露区(铅锌矿区某冶炼厂区)和远离高铅暴露区儿童分别作为观察组和对照组,采用问卷调查、体格检查(包括钙含量、是否脱发、是否贫血和是否易患感冒)和智商测定(VIQ、PIQ及FIQ)的方法调查分析高铅暴露对儿童齿铅水平、体格发育,以及智商的影响。结果观察组儿童齿铅含量、脱发和贫血阳性率分别是(60. 8±15. 3)μg/g、48. 73%和47. 2%,均明显高于对照组(P<0. 05)。VIQ、PIQ及FIQ得分均比对照组低(P<0. 05)。结论生活在高铅暴露区的儿童智力和生长发育均受到铅暴露的严重影响。     

铅挤压阻尼器的试验研究

铅具有良好的塑性变形能力,变形后能重新结晶恢复、无应变硬化。基于该特征,制作了铅挤压阻尼器,通过试验研究了铅阻尼器在不同振幅、不同频率组合下的力学性能。试验结果表明,铅挤压阻尼器的滞回曲线丰满,耗能效率高,工作性能稳定,可以作为建筑结构风振和抗震控制的消能装置。     

Lead and traditional Moroccan pharmacopoeia.

The use of traditional cosmetics and remedies such as kohl and henna is very common in Morocco, especially among women, children and babies. Kohl is a dangerous eye cosmetic. It is usually mixed with other harmful substances, then applied on women's eyebrows and used in skin treatments for infants. Henna is another traditional product, with religious associations, which has been widely used over the centuries for cosmetic and medical purposes. Many people add various herbs or other substances to the henna in order to strengthen it or to give it a stronger colour. Our results were reassuring in that the concentrations of lead found in non-elaborate (henna only) samples of henna were low. However, when henna was mixed with other products (elaborate henna), these concentrations increased. Lead concentrations in kohl were very high however, unlike henna, were lower in mixed kohl as mixing with other products diluted the concentration of lead. Nevertheless, in both types of kohl, lead concentrations were very high and consequently constitute a risk for public health, particularly for children.     

Lead contamination of inexpensive plastic jewelry

The neurological hazards of lead to children are well-known. As a result of recent documented cases of lead poisoning, regulatory attention in the United States has focused on the lead content of children's metal jewelry. By contrast, little is known about the possible hazards of plastic jewelry items. The objective of this study was to determine whether inexpensive plastic jewelry is a possible source of toxic lead for children. Samples of more than 100 inexpensive plastic jewelry items were analyzed for lead content. Beads were screened by soaking in 1 M nitric acid. Nine items found to release more than 30 microg of lead per bead were further tested for accessible lead, and scrapings of the bead coatings were analyzed for total lead content. The maximum accessible lead found was 49 microg per bead, which is below the current US Consumer Product Safety Commission limit of 175 microg. However, when the number of beads in each item was taken into account, six of the nine leaded samples contained more than 175 microg accessible lead per item. The lead in these items appears to be associated with lead-based paints used to produce glossy coatings on imitation pearls and similar items. Coatings obtained by scraping individual beads contained 3.5-23% lead, which far exceeds the US regulatory limit of 0.06% lead in paints on items intended for children. Our results demonstrate that plastic jewelry items merit the attention of public health and consumer protection agencies seeking to limit the exposure of children to lead.     

Lead modelling — A decision-making tool

The difficulties of decision-making in a state of ignorance regarding the problem area, true for many questions of environmental pollution, are discussed with reference to lead. Before irrevocably committing a considerable amount of both capital and material resources, the policy-maker would like to make a prediction as to the potential effectiveness of any control measure. To this end a mathematical model is suggested which represents the transport of lead within a standard man. It may be used at two discrete levels, either to analyse a number of control strategies in terms of their relative effectiveness in reducing blood lead concentrations, or, dependent upon the model's accuracy and the availability of data concerning the exposure to, and metabolism of, lead by a specific population, to select between two, or more, directly competing strategies for the control of that population's lead exposure, the selection of the optimum strategy being based on the model's output. Modelling may be seen, therefore, to satisfy, at least in part, the need for decision-making information in an area where time may not permit the acquisition of appropriate, unequivocable scientific evidence.     

大景观和可持续发展

1.大景观 将要从业的学生们、年轻人,想要从事的已经不是原来的行业的范畴.这不仅是处理视觉、尺度、色彩的问题,而是要处理更大的环境--城市环境及人类居住与自然环境之间的关系问题.所以用大景观,也许有的学者会反对,因为大小只是一个形容词,但它背后代表着严谨的意思,它背后所代表的正是当今景观发展的方向,就是景观这个行业所涵盖的范围越来越大,它在社会发展和城市建设起到的作用越来越重要,它的触角已经伸到了其他的行业中.无论是大地规划、地理规划、传统的园林设计、法国的宫廷园林,都包括一个大景观的思路,我们应该用比较包容的态度来看待整体的行业.