Nonaqueous titration of functional groups in humic acid     

Koyo Yonebayashi  Tomoo Hattori 《Organic Geochemistry》1985,8(1):47-54

Humic acid was titrated by sodium methoxide in dimethylsulfoxide using platinum-calomel electrode systems. Adding benzoic acid and phenol as internal standards to humic acid yielded two inflections. The titer at the first inflection point was equivalent to the carboxyl groups whose pK_a (H₂O) values were less than 7. The difference between the titers at the two inflection points was equivalent to the phenolic hydroxyl groups whose pK_a (H₂O) values were 7–10. Calculated results for the carboxyl and phenolic hydroxyl groups in humic acid obtained by the nonaqueous titration method agreed closely with those obtained by conventional methods.  相似文献   

用微波封闭溶样氢醌滴定法快速测定金   总被引：5，自引：0，他引：5  

薛光  张汝生  姚万林  刘永生 《黄金地质》2003,9(3):69-71

采用HNO3—NaCl^--MnO2-NK4HF2溶样体系，在微波场中对矿样进行封闭溶解。实验表明，称样20g，利用聚丙烯溶样瓶，在微波场内只要照射2～3min，即可将矿样中的Au完全分解，以活性炭进行吸附富集，氢醌滴定法进行测定，其分析结果可满足地质找矿和选冶工艺对Au分析的要求。  相似文献   

高岭石表面酸碱反应的电位滴定实验研究   总被引：2，自引：0，他引：2       下载免费PDF全文

高嵩何广平  吴宏海孙伟亚 《岩石矿物学杂志》2005,24(3):239-244

采用表面酸碱电位滴定法探讨高岭石表面酸碱性质,基于多位模式(即假定高岭石表面存在3种基团Al2 OH 、AlOH 和SiOH ) ,根据实验所得数据对高岭石表面的质子化和去质子化过程的相关参数进行拟合,讨论各个位点所发生的反应,并探讨了支持电解质浓度、高岭石溶解过程对表面酸碱电位滴定结果的影响。高岭石的表面零净质子电荷点(pHPZNPC,5 .2 )不等同于零电荷点,当pH <5 .2时,高岭石表面荷正电荷,主要由于表面富硅贫铝层的形成和Al位的质子化所致;当pH >5 .2时,高岭石表面荷负电荷,以Si位和Al的去质子化反应为主。  相似文献   

Determination of the Concentration of Carbonic Species in Natural Waters: Results from a World‐Wide Proficiency Test          下载免费PDF全文

Mahendra P. Verma  Enrique Portugal  Sophie Gangloff  María Aurora Armienta  Dornadula Chandrasekharam  Mayela Sanchez  Roberto E. Renderos  Miguel Juanco  Robert van Geldern 《Geostandards and Geoanalytical Research》2015,39(2):233-255

The results of an international interlaboratory proficiency test for the determination of carbonic species are presented. Eight laboratories analysed twelve water samples (four synthetic waters, one lake water, four geothermal waters, one seawater and two petroleum waters) by two methods: (a) individual laboratory analytical procedure and (b) acid–base titration curves in tabular form following a standardised protocol. In case (b), the concentrations of carbonic species were calculated by the organiser using the (1) Hydrologists' method, (2) Geochemists' method and/or (3) initial pH and total alkalinity method. For synthetic waters, the averaged % trueness and precision of measurement of the two methods were (trueness = 7.6, precision = 9.4) and (9.0, 3.4) for total alkalinity, and (6.6, 31.0) and (7.8, 6.1) for carbonic alkalinity, respectively. This indicates that the total alkalinity calculation procedure is in general correct in the individual laboratory method, but the carbonic alkalinity calculation procedure has serious problems. The measurements of total alkalinity for lake and seawaters were in agreement in both the methods; however, the individual laboratory measurement method for geothermal and petroleum waters was conceptually incorrect. Thus, the analytical procedures for the determination of carbonic species were reviewed. To apply the Hydrologists' and/or Geochemists' methods, the location of NaHCO₃EP and H₂CO₃EP is necessary, even for samples with pH lower than that of NaHCO₃EP, and a backward titration curve after complete removal of CO₂ must be performed. The initial pH and total alkalinity method is appropriate where a complete analysis of species that contribute to the alkalinity is known.  相似文献   

STUDY ON DETERMINATION OF DIC IN SEAWATER BY COULOMETRIC METHOD     

纪雷  陆贤昆 《中国海洋湖沼学报》1997,15(4):357-362

lareODUcrIONThetotalcarbondi0xideisandriportantparametrforestirnatingthespatiotem0ralinorganiccarbontransport,andanthropogeniccarb0ndi0xideincreasesintheoonn.Ap~coulomericednique(MethodG0fASTMD5l3-82)formeasuringDICinanwaterdevelopedbyJohnsonetal.(l985)istheshipkoardmehodchosenfortheglobeocanicinofganiccarb0nsurveyt0bemadeinconjunCtionwiththeW0riddrinCirmlationExperirnentWorklHydrographicProgram(WOCEWHP)andtheJointGobal~nFluxStudy(JGOFS)program(Catherine,G.etal.,l993).Thecruxof…  相似文献   

POTENTIOMETRIC TITRATION OF CALCIUM IN SEAWATER   总被引：2，自引：0，他引：2  

谢式南  纪红  吴爱琴  陈国华 《中国海洋湖沼学报》1997,15(1):32-35

Atpasent,thestandardmethodfordetendningcalciuminseawateriscomPlexometrictitrationusingEGTA[ethyleneglycol-bis(2-adrinoethylether)-N,N,N',N'-tetraaceticacid]andGHAtelyoxal-bis(2-hydroxyanil)].ThisInethodwasfirStdeveopedbyTSunogaietal.(l968),sumrnarindbyKremling,andeditalinMethodsofSeawaterAnalySisbyGrasshoff(l983).AlthoughtheendpointreadingsinthismethodarenotquitCsharp,andrnaybeaffCCtedbyoveanstweather,withtheuseofcalctumISEasindicatingeledrode,SCEasreferenceeledrodeanddigitalvoltme…  相似文献   

自动电位滴定测定锰矿石中锰的方法研究   总被引：3，自引：3，他引：0  

马德起  谷松海  张国胜  吴瑶  韩娟 《岩矿测试》2013,32(4):595-599

多批次的锰矿石锰含量滴定分析消耗大量人工,随着自动化电位滴定仪的普及,利用仪器完成容量滴定成为可能,而将手工滴定向自动电位滴定移植是当前需要解决的课题。本文建立了一套自动电位滴定仪测定锰矿石中锰含量的方法,确定了相关滴定参数和等当点识别标准。锰矿石样品采用盐酸、磷酸分解,硝酸去除碳和有机物,高氯酸氧化,形成样品溶液。自动电位滴定仪先用硫酸亚铁铵标准溶液对预先移取的重铬酸钾标准溶液和标定空白溶液分别进行氧化还原滴定,用铂复合电极指示,计算得到硫酸亚铁铵标准溶液浓度,再对样品空白溶液和样品溶液进行氧化还原滴定,得到样品锰含量,方法检测范围为5%～60%。采用本法分析国家一级标准物质,测定结果的准确度和精密度高;分析多个产地不同水平的锰矿石样品,测定结果与手工方法进行对照,经t检验无显著性差异。建立的滴定方法自动化程度高、方法稳健,适用于冶炼企业、港口商检等行业,具有推广价值。  相似文献   

溶液中钙镁含量准确测定的方法研究          下载免费PDF全文

武涵  俞秀丽  吴晓娅  付晓艺  尹霞  曾德文 《盐湖研究》2013,(4):29-33

经典测定钙、镁含量的方法是用EDTA标准溶液滴定钙镁总量后再滴定钙,此方法对于含钙、镁离子盐水体系溶解度的测定,尤其在镁含量较高的情况下,其分析精度和准确度远远迭不到要求。针对硝酸钙、硝酸镁混合样品,采用EDTA质量滴定法测定钙镁总量,用草酸钙沉淀法从镁中定量分离钙,然后运用羔减法计算出镁的含量。实验结果表明,当混合溶液中镁钙的质量比不超过10：1时,钙、镁离子分析结果的相对误差在±0．3％之内,但镁钙的质量比超过10：1时,相对误差达到1％。因此,在一定的镁钙质量比范围内,此方法可用于盐水体系中钙、镁含量的准确测定。  相似文献   

高钙低镁体系中钙镁测定方法的改进研究          下载免费PDF全文

李波  祁米香  王舒娅  唐宏学  赵增兵  杨占寿  邹兴武 《盐湖研究》2013,(4):34-36

EDTA络合滴定法是应用范围比较广的传统方法,但该方法对样品中钙镁摩尔比的适用范围约为1：10-10：1,时于超过该范围的钙镁比样品测定的准确度会有所下降;传统EDTA络合指示剂滴定法测定高钙低镁体系中钙镁含量时,终点不易判断,测定结果平行性差,甚至出现钙镁总量小于钙量的情况。通过往样品中加入一定量Mg’标准溶液的方法,改善了滴定反应效果。结果表明,Mg^2＋的加入能明显提高滴定终点变色灵敏度。加标回收试验表明,镁的回收率达到99．96％,钙的回收率达到99．40％。该方法准确度高,操作简单,适用性强。  相似文献   

海水中钙的电位滴定     

谢式南  陈国华  王建华 《中国海洋大学学报(自然科学版)》1998,(4)

钙离子选择性电极为指示电极,饱和甘汞电极作参比,用硼砂盐缓冲液控制ｐＨ,以ＥＧ－ＴＡ为滴定剂进行电位滴定。与现行用ＧＨＡ为指示剂、ＥＧＴＡ为滴定剂的络合滴定法相比,可减小络合滴定中目测终点的人为误差,故测量精度优于０．０８％。  相似文献