Indirect complexometric determination of beryllium

An indirect complexometric method is described for the determination of beryllium, which is selectively precipitated as Be(NH(4))PO(4), then dissolved in HCl, and the solution passed through an ion-exchange column to retain Be and allow PO(4)(3-)to pass through. Phosphate is precipitated as Mg(NH(4))PO(4) and Mg in the precipitate is titrated with EDTA. Be is obtained from the Mg content.     

Indirect complexometric determination of chromate

Chromate is determined indirectly, by precipitation as silver chromate, dissolution of the precipitate in potassium tetracyanonickelate, and titration of the liberated nickel with EDTA, with Murexide as indicator.     

Indirect complexometric titration of sodium and potassium with EDTA

Summary Sodium is precipitated as sodium zinc uranyl acetate, filtered and dissolved in water, and zinc is titrated with EDTA using eriochrome black T as indicator. Potassium is precipitated as potassium sodium cobaltinitrite and dissolved in hot water containing little hydrochloric acid. The blue colored solution produced by cobalt in solution, with ammonium thiocyanate and acetone was titrated with EDTA until colorless. The results are good.The author is grateful to Prof. Philip W. West, Boyd Professor of Chemistry, Louisiana State University, for kindly providing the facilities to carry out the investigation.     

Direct complexometric titration of thorium with versene using SPADNS

Summary The existing volumetric methods for the determination of thorium are indirect and unsatisfactory. A direct titrimetric method for the estimation of thorium has been developed which involves the adjustment ofph, addition of 1 ml. of 0.02% SPADNS indicator, dilution to volume and titration with versene. It is based on the fact that thorium forms a coloured complex with SPADNS and after the bulk of thorium has reacted with versene, the highly coloured thorium- indicator complex is destroyed, marking the end point. Quantity of thorium as small as 5 mg. can be titrated accurately when present in a volume of 50 ml. Determination of thorium can also be made in presence of large amount of iron by adding ascorbic acid prior to the titration. Interferences of various ions have also been studied. The method proposed for thorium is selective and should be of considerable use in many cases.The author's thanks are due to Dr. A. K. Ghosal, Principal Darjeeling Government College, for providing all laboratory facilities and Dr. A. K. Mukherjee, Indian Association for the Cultivation of Science, Calcutta for his kind help in the work.     

Chemical analysis of archaeological copper and brass fron northeastern Ontario

Since it is now possible, with some reliability, to separate native from European copper using chemical analysis, we now sort archaeological copper into geological (North American) or smelted (European) groups and thereby help address issues relating to the cultural impact of earliest aboriginal — European contact in northeastern Ontario. Twenty six metal samples from 11 archaeological sites, dating from the 17th to 19th centuries, were analyzed by INAA. The results were compared with reference data for native copper and European trade copper and indicate that of the 17 copper samples in the suite, an archaeologically-unexpected high number of 12 were made of native copper. The majority of these samples (7 of 8) derived from the post-contact early 17th century Providence Bay Odawa village. The remaining samples were made of brass (8) and zinc (1). Two of the brass samples, from Point Louise, have remarkably similar chemistries and probably came from the same object, or at least from the same batch of brass.     

Selective complexometric determination of palladium with thiosulphate as masking agent

A selective complexometric method is suggested for the determination of palladium, sodium thiosulphate being used as releasing agent. To a solution containing palladium and other cations, excess of EDTA is added and the surplus is back-titrated with lead nitrate solution at pH 5-5.5 in sodium acetate buffer with Xylenol Orange as indicator. EDTA equivalent to palladium is then released quantitatively with sodium thiosulphate and is titrated with the lead nitrate solution. The interference of various cations has been studied and the method applied for the analysis of alloys.     

Selective complexometric determination of mercury with thiocyanate as masking agent

A method is proposed for selective complexometrie determination of mercury, thiocyanate being used as masking agent. An excess of EDTA is added and the surplus is back-titrated at pH 5-6 with lead nitrate, Xylenol Orange or Methylthymol Blue being used as indicator. Thiocyanate is then added to decompose the mercury-EDTA complex and the liberated EDTA is titrated with lead nitrate. The interference of various cations has been studied.     

The determination of copper by complexometric titration with ethylenediaminetetraacetic acid

A method has been developed for the determination of cupric copper by complexometric titration with ethylen.ediaminetctraacetic acid. The titrations were followed potentiometrically, and were effected at pH 5–6 in the presence of an ammonium acetate buffer. Interfering metals such as ferric iron, aluminium, cadmium, zinc, manganese, nickel, cobalt and lead must be removed by a preliminary separation.     

Graphical evaluation of complexometric titration curves

A graphical method, based on logarithmic concentration diagrams, for construction, without any calculations, of complexometric titration curves is examined. The titration curves obtained for different kinds of unidentate, bidentate and quadridentate ligands clearly show why only chelating ligands are usually used in titrimetric analysis. The method has also been applied to two practical cases where unidentate ligands are used: (a) the complexometric determination of mercury(II) with halides and (b) the determination of cyanide with silver, which involves both a complexation and a precipitation system; for this purpose construction of the diagrams for the HgCl(2)/HgCl(+)/Hg(2+) and Ag(CN)(2)(-)/AgCN/CN(-) systems is considered in detail.     

Selective complexometric determination of palladium, with thiourea as masking agent

A method is proposed for selective complexometric determination of palladium, thiourea being used as masking agent. An excess of EDTA is added and the surplus EDTA is back-titrated at pH 5-5.5 with lead nitrate, with Xylenol Orange as indicator. Thiourea is then added to decompose the palladium-EDTA complex and the liberated EDTA is again back-titrated with lead nitrate. The interference of various cations has been studied.     

Selective complexometric determination of mercury with sulphite as indirect masking reagent

A complexo-titrimetric method for the determination of mercury(II) in the presence of other metal ions is described, based on the selective masking ability of sulphite ion towards Hg(II). Mercury in a given sample solution is initially complexed with a known excess of EDTA and the surplus EDTA titrated with zinc sulphate solution at pH 5.0–6.0 (hexamine), using xylenol orange (or methylthymol blue) as indicator. An excess of solid sodium sulphite is then added to decompose the Hg(II)-EDTA complex and the released EDTA is titrated with standard zinc sulphate solution. Reproducible and accurate results are obtained for 9.9–99 mg Hg with relative errors < 0.35% and standard deviations < 0.05 mg. The effects of various cations and anions are studied.     

Selective complexometric determination of tin, with mercaptans as releasing agents

A method is proposed for selective complexometric determination of tin, mercaptans being used as releasing agents. To a solution containing tin and other cations, excess of EDTA is added and the surplus is back-titrated at pH 5-6 with lead nitrate (Xylenol Orange as indicator). Thioglycollic acid or mercaptopropionic acid is then added to decompose the tin-EDTA complex and the liberated EDTA is titrated with lead nitrate. The interference of various cations has been studied and the method has been employed for the estimation of tin in a variety of alloys.     

Fibre-optic titrations-IV Direct complexometric titration of aluminium(III) with DCTA

The end-point of the direct complexometric titration of Al(3+) in pH 4.6 solution can be determined by monitoring the fluorescence intensity of the aluminium-morin complex, by use of a bifurcated fibre-optic light guide. The method allows the determination of aluminium in the 1-800 ppm range with good precision. The procedure is applicable even when the solutions are strongly coloured or turbid, but because of the slow complexation kinetics requires a titration time of about 20 min.     

Indirect complexometric determination of small amounts of tellurium

Summary A complexometric method is proposed for the determination of small amounts of tellurium (50–350g). It is based on the reaction between Te(IV) and diethyldithiocarbamic acid (DDTC). The compound of the composition Te(DDTC)₄ obtained is extracted with CCl₄ at p_H 8.7–8.8. The yellow organic extract is shaken with copper(II)-ammonia solution, p_h 11. The organic phase, containing Cu(DDTC)₂ is then shaken with silver-ammonia solution. The Cu(II)-ions pass into the aqueous phase where they are titrated with 0.002M EDTA, using glycinethymol blue as indicator. Selenium(IV) does not interfere.

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Zusammenfassung Die Reaktion zwischen Te(IV) und Diäthyldithiocarbaminsäure (DDTC) wurde zur komplexometrischen Bestimmung kleiner Mengen Tellur (50 bis 350g benützt. Te(DDTC)₄ wird mit CCl₄ extrahiert (p_H 8,7 bis 8,8) und der gelb gefärbte organische Extrakt mit ammoniakalischer Cu(II)-Lösung bei p_h11 ausgeschüttelt. Dabei findet ein Austausch von Te(IV) gegen Cu(II) statt. Die Cu(II)-Ionen der organischen Phase werden mit ammoniakalischer Ag(I)-Lösung umgesetzt und gehen in die wäßrige Phase über, wo sie mit 0,002-m ÄDTA-Lösung gegen Glycinthymolblau titriert werden. Selen(IV) stört nicht.

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Résumé On propose une méthode complexométrique pour le dosage de petites quantités de tellure (50-350g). Elle est fondée sur la réaction entre Te-IV et l'acide diéthyldithiocarbamique (DDTC). On extrait par CCl₄ á p_H 8,7–8,8 le produit obtenu, de composition Te(DDTC)₄. On agite l'extrait organique jaune avec une solution ammoniacale de cuivre-II. Les ions cuivriques passent dans la phase aqueuse oú ils sont titrés par l'EDTA 0,002M, avec le bleu de glycinethymol comme indicateur. Le sélénium-IV n'interfére pas.

     

Rapid biomass analysis

New, rapid, and inexpensive methods that monitor the chemical composition of corn stover and corn stover-derived samples are a key element to enabling the commercialization of processes that convert stover to fuels and chemicals. These new techniques combine near infrared (NIR) spectroscopy and projection to latent structures (PLS) multivariate analysis to allow the compositional analysis of hundreds of samples in 1 d at a cost of about $10 each. The new NIR/PLS rapid analysis methods can also be used to support a variety of research projects that would have been too costly to pursue by traditional methods.