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Journals publishing articles in analytical chemistry: 2004 list


Journals publishing articles in analytical chemistry: 2004 list


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Russian journals publishing articles in analytical chemistry are almost wholly covered by the Science Citation Index.


Shchelkunov (Siberian University Publishing, 2004)

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 In view of the necessity of a rapid and accurate process for the determination of fluorine applicable in the analysis of sodium fluoride and otherfluorine compounds,the author has established a new volumetric processconsisting in the titration in aqueousalcoholic medium with ferric nitrate asstandard solution and sodium salicylate as indicator.All of the methods,published by Guyot,Greeff,Fairchild andVisintin proposed for the determination of fluorine using ferric solutionas standard,are based on the... In view of the necessity of a rapid and accurate process for the determination of fluorine applicable in the analysis of sodium fluoride and otherfluorine compounds,the author has established a new volumetric processconsisting in the titration in aqueousalcoholic medium with ferric nitrate asstandard solution and sodium salicylate as indicator.All of the methods,published by Guyot,Greeff,Fairchild andVisintin proposed for the determination of fluorine using ferric solutionas standard,are based on the reaction:6NaF+FeCl_3→Na_3FeF_6+3NaCl. But the sodium ferric fluoride thus formed is fairly soluble in water and makesthe endpoint unclear,therefore the titration can not be performed accurately.This seems to be due to the fact that the following two reactions advancesimultaneously,and accordingly the formation of sodium ferric fluoride is incomplete in aque(?)us medium:3NaF+Fe(NO_3)_3→FeF_3+3N_aNO_33NaF+FeF_3→Na_3FeF_6Nevertheless,these reactions,according to the author's experiments;proceedalmost quantitatively in meda.containing at least 50% by volume of alcohol.This paper reports the xperimental results obtained in the fundamentalstudies on the various factors influencing the accuracy of the volumetry,namely,the sensitivity and the necessary amount of sodium salicylate used asindicator,the pH value,the alcoholic concentration of the titration medium,the concentration of the fluoride taken for the determination and the timewhen alcohol should be added in the course of titration.Furthermore,a rapidvolumetric process with high accuracy is proposed together with its applicationsin ordinary analyses of sodium fluoride and other fluorine compounds.The proposed method is characteristic in using sodium salicylate asindicator,which shows sharp violet color with minute amount of ferric ion inmedium of pH 3 controlled with buffer solution,then titrating with standardferric nitrate,and adding proper amount of alcohol(the alcoholic concentration at the endpoint should be above 50%)during the titration,when themedium becomes orange yellow in color.The method may be summarized as follows:Take 5 ml of neutral sodiumfluoride solution of about 0.3 N in a small Erlenmeyer flask,add 2.5 mlof Walpole's buffer solution of pH 3(formed by dissolving 34.0 g ofcrystalline sodium acetate and 20 ml of 38% HCl in water,and making upto 250 ml)and 1 ml of 0.1 M sodium salicylate dissolved in 50% alcohol.After sufficient stirring,titrate with standard 0.3 N(0.05 M)ferric nitratesolution,using microburette until the medium becomes orange yellow,thisstep being reached after addition of about 4 ml of titrant.Then decolorizethe solution by adding 12.5 ml of absolute alcohol(or 13 ml of 95% alcohol),previously purified by redistillation with lime;stirring is necessary during theaddition.Further continue the titration until the light pink color formeddoes not fade after stirring for 30 seconds when observed over a white surface. In the analyses of sodium fluoride and other fluorine compounds containing interfering substances,such as divalent and polyvalent metallic ions,phosphate,silicate,borate,carbonate,sulfide ions and reductants acting on ferricion,it is necessary to separate fluorine from these interfering substances bythe distillation with sulfuric acid according to the method of Willard andWinter(20).Then the distillate is neutralized with dilute sodium hydroxideand adjusted to the proper pH with hydrochloric acid using pnitrophenol asindicator.The solution is ready for titration as described.But in the caseof absence of these interfering substances except carbonate,for example,inthe determination of the concentration of sodium fluorde solution obtained bythe extraction of the crude product,produced industrially by fusing fluorsparwith sodium carbonate and silica,the above separation of fluorine by distillation is dispensable.The anaIytical results obtained by the proposed method are in goodagreement with those obtained by the lead chlorofluoride process(8),whichis recognized as official method for the determination of fluorine in agriculturalproducts.  本文介绍一容量分析氟的新方法和在工业制品上的应用,并分析了一种工业制备的氟化钠液,所得的结果和氟氯化铅法所得的极为一致。对于影响该分析法准确度的各种因素:指示剂的灵敏度和滴定时适宜的用量、溶液的 pH 值、应加的乙醇量、操作中加乙醇的次序、以及氟离子的适宜浓度,均加以研究并找出适宜的情况。本法用硝酸铁为标准液,水杨酸钠作指示剂,在 pH=3左右作滴定;当溶液呈橙黄色时,加入适量的乙醇,使其浓度在终点时仍不低于50%。如有干扰物质如二价及多价金属离子、磷酸根、矽酸根、硼酸根、碳酸根、硫化物和还原物质可能与三价铁起作用者,均应分离之。  The effects of copper and zinc ionsupon the precipitation of barium sulphate have been noted for a long time.However,the results published wereeither not systematic(3,4b,5,6)or obtained under conditions apart fromusual analytical practice(7,8).Thus,it seems necessary to investigate thissubject in more detail by the usual methods of determination.The presentcommunication reports(a)the effect of various amounts of cupric and zincions and(b)the influence of different acidities during precipitation in thepresence... The effects of copper and zinc ionsupon the precipitation of barium sulphate have been noted for a long time.However,the results published wereeither not systematic(3,4b,5,6)or obtained under conditions apart fromusual analytical practice(7,8).Thus,it seems necessary to investigate thissubject in more detail by the usual methods of determination.The presentcommunication reports(a)the effect of various amounts of cupric and zincions and(b)the influence of different acidities during precipitation in thepresence and absence of zinc ions.It is found that the interference of copper in the determination of sulphuras barium sulphate up to a ratio of 20:1 for Cu:S is negligible.The deviationsof the results obtained from theoretical values are all within ±2‰(see Table1),and do not show any regularity with the amount of copper added.The presence of zinc ions alone gives satisfactory results(slightly lowerthan theoretical values).As the amount of zinc ions in solution increases,thedeviations become somewhat wider(Table 2).The low results are presumedto be due to(1)the formation of soluble zincsulphate complex,which holdsa part of sulphate in solution,and/or(2)diverse ion effect.In the presenceof zinc ions,introducing hydrochloric acid up to 0.1 N before precipitationcauses essentially the same errors as if hydrochloric acid were absent(cf.Tables2 and 3),while at and beyond 0.2 N positive errors are obtained.A spectrographic examination of the precipitates reveals that zinc doescoprecipitate with barium sulphate,though only to a slight extent.The amountof zinc coprecipitated decreases with the increase of the acidity of the solutionfrom which the precipitate is thrown down.  本文报告铜及锌离子对于硫酸钡定硫的影响,找出了铜的影响几近于零,锌的影响亦微。锌离子能与硫酸钡共同沉淀。  This paper is a supplement to the author's previous paper "The Constants and Analysis of Rigid Frames", published in the first issue of the Journal. Its purpose is to amplify as well as to improve the method of propagating joint rotations developed, separately and independently, by Dr. Klouěek and Prof. Meng, so that the formulas are applicable to rigid frames with nonprismatic bars and of closed type. The method employs joint propagation factor between two adjacent joints as the basic frame constant... This paper is a supplement to the author's previous paper "The Constants and Analysis of Rigid Frames", published in the first issue of the Journal. Its purpose is to amplify as well as to improve the method of propagating joint rotations developed, separately and independently, by Dr. Klouěek and Prof. Meng, so that the formulas are applicable to rigid frames with nonprismatic bars and of closed type. The method employs joint propagation factor between two adjacent joints as the basic frame constant and the sum of modified stiffness of all the barends at a joint as the auxiliary frame constant. The basic frame constants at the left of right ends of all the bars are computed by the consecutive applications of a single formula in a chain manner. The auxiliary frame constant at any joint where it is needed is computed from the basic frame constants at the two ends of any bar connected to the joint, so that its value may be easily checked by computing it from two or more bars connected to the same joint.Although the principle of this method was developed by Dr. Klouěek and Prof. Meng, the formulas presented in this paper for computing the basic and auxiliary frame constants, besides being believed to be original and by no means the mere amplification of those presented by the two predecessors, are of much improved form and more convenient to apply.By the author's formula, the basic frame constants in closed frames of comparatively simple form may be computed in a straightforward manner without much difficulties, and this is not the case with any other similar methods except Dr. Klouěek's.The case of sidesway is treated as usual by balancing the shears at the tops of all the columns, but special formulas are deduced for comput ing those column shears directly from joint rotations and sidesway angle without precomputing the moments at the two ends of all the columns.In the method of propagating unbalanced moments proposed by Mr. Koo IYing and improved by the author, the unbalanced moments at all the barends of each joint are first propagated to the barends of all the other joints to obtain the total unbalanced moments at all the barends, and then are distributed at each joint only once to arrive at the balanced moments at all the barends of that joint. Thus the principle of propagating joint rotations with indirect computation of the barend moments is ingeneously applied to propagate unbalanced moments with direct computation of the barend moments, and, at the same time, without the inconvenient use of two different moment distribution factors as necessary in all the onecycle methods of moment distribution. The basic frame constant employed in this method is the same as that in the method of propagating joint rotations, so that its nearest approximate value at any bar end may be computed at once by the formula deduced by the author. Evidently, this method combines all the main advantages of the methods proposed by Profs.T. Y. Lin and Meng ChaoLi and Dr. Klouěek, and is undoubtedly the most superior onecycle method of moment distribution yet proposed as far as the author knows.Typical numerical examples are worked out in details to illustrate the applications of the two methods.  本文為著者前文“剛構常數與剛構分析”之補充,其目的在將角變傳播法及不均衡力矩傳播法加以改善,以便實用。此二法均只需一個公式以計算剛構中所有各桿端之基本剛構常數(即任何二相鄰結點间之角變傳播係數),將此項公式與柯勞塞克之公式相比較,藉以指出前者較後者為便於應用,並亦可用之以直接分析較簡單之閉合式剛構,此外補充說明此法中之剛構常數與定點法之關係,剛構有側移時計算各結點角變所需之各項公式亦行求出。不均衡力矩傳播法係顧翼鹰同志最近研究所得者,既係直接以桿端力矩為計算之對象,而且只須採用不均衡力矩分配比將各結點作用於各桿端不均衡力矩之總和,一次分配,即得所求各桿端分配力矩之總值,實係力矩一次分配法之一大改進,著者將顧氏之法加以推廣与改善,使其原則簡明而計算便捷,著者認為此法係將林、柯、孟三氏法之所有優點熔冶於一爐,實可稱為现下最優之力矩一次分配法。最後列舉算例,以說明此二法在實際工作中之應用。   << 更多相关文摘 
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