Spectrophotometric determination of niobium and its application to niobium-stabilized stainless steel

A spectrophotometric method is described for the determination of niobium by means of its reaction with tannin and thioglycollic acid. The yellow-orange colour developed with the reagent mixture at pH 4 is measured at 410-420 nm and obeys Beer's law between 0.5 and 10 ppm niobium. The method is suitable for the determination of niobium in niobium-stabilized stainless steel and other types of steels containing niobium, but a prior separation of niobium is necessary. Titanium interferes even in traces.     

Contributions to the basic problems of complexometry—VIII Thioglycollic acid as a masking agent

The masking properties of thioglycollic acid (TGA) as well as the possibilities of its use in complexometry have been studied. It has been found that thioglycollic acid in an alkaline medium perfectly masks metals such as Pb, Bi, Cd, Ag, Hg, Zn, Tl, In and Sn because of the formation of colourless complexes. In this medium TGA forms intensely coloured complexes with Fe, Co and Ni. The red coloration of the Fe-TGA complex can be prevented by the addition of triethanolamine. It has been found that the Ni- and Co-EDTA complexes do not react with TGA. This enables a highly selective determination of nickel and cobalt to be made. Also, manganese can be determined in the presence of other metals screened with TGA. The advantages of TGA in comparison with potassium cyanide are discussed.     

Study of the molecular absorption spectrometric determination of phosphorus in steel, nickel base alloys and zircaloy using the yellow phosphovanadomolybdate complex

Summary The molecular absorption spectrometric method using the yellow phosphovanadomolybdate complex,adopted as ISO-standard for determination of phosphorus in steel, has been optimized.High and varying blank values often reported in literature were found to be due to silicon interference. The silicon is released from the glass beaker during fuming with perchloric acid and the problem is avoided by either using teflon beakers or by adding hydrofluoric and boric acid after fuming.Interferences from elements present in the metal (arsenic, chromium, silicon and the refractory elements) were quantified and procedures are described for masking these interferences in order to make the method applicable to high-alloy steels, tool steels, nickel-base alloys and Zircaloys. Arsenic, hafnium, niobium, tantalum and tungsten cause the most severe interferences. Chromium, titanium and zirconium were found to have weak interferences whereas molybdenum and silicon did not interfere at all despite large amounts of precipitated oxides.Results reported by other authors that many old certified reference materials of low-and high-alloy steels have too high certified phosphorus values were confirmed with the described method as well as with the ICP-OES technique. However, the lower values were only found for alloys without Hf, Nb, Ta or W. Alloys containing these elements were often found to have higher phosphorus values, which reflects interferences not completely removed in the previous analyses of these alloys.

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Untersuchung der molekularabsorptions-spektrometrischen Phosphorbestimmung auf Grund des gelben Phosphovanadomolybdat-Komplex in Stahl, Nickellegierungen und ZircaloyPhosphorbestimmung in Referenzmaterialien

     

The determination of titanium in alloys by atomic absorption spectroscopy

A method is described for the determination of 0.1–1.2 % of titanium in steels, permanent magnet alloys and cast iron using atomic absorption spectroscopy with hydrofluoric acid solutions and a nitrous oxide-acetylene flame. No preliminary separations are required. When the correct conditions are employed there is no interference from the other elements commonly found in these alloys.     

Extractions with long-chain amines-III: colorimetric determination of molybdenum as thioglycollate

A highly selective and sensitive colorimetric determination of molybdenum(VI) based on its extraction with a chloroform solution of trioctylamine from solutions of acetic and thioglycollic acid (TGA) is described. The yellow chloroform extract containing the molybdenum-TGA complex is measured at 370 nm. With a single extraction it is possible to determine small amounts of molybdenum in the presence of very large concentrations of almost all metals. Only bismuth, mercury and tungsten interfere.     

Colorimetric determination of niobium in titanium alloys

There is need for a method for the determination of niobium in titanium alloys, since niobium-titanium alloys are becoming increasingly important. The determination of niobium in this type of alloy is an extremely difficult matter. Many approaches were tried before the problem was solved. In the method proposed in this paper the sample is dissolved in a mixture of hydrofluoric and nitric acids, the solution evaporated to a small volume, and boric acid added. Two tannic acid separations are then made to separate the niobium from the bulk of the titanium. The niobium, is determined colorimetrically by the thiocyanate method using a water-acetone medium. A study was made of the possible interference of elements that might be present in titanium alloys. It was found that the presence of tantalum causes two opposing tendencies. Tantalum can cause high results for niobium because it forms a complex with thiocyanate which is visually colorless but shows some absorption. Tantalum can cause low results for niobium by hindering the development of the niobium color. The resultant effect of the tantalum depends upon the amount of tantalum present, the amount of niobium present and the ratio of tantalum to niobium. The presence of more than one per cent. tungsten can lead to high results for niobium. Other elements that might be present in titanium alloys do not interfere with the method. The procedure is designed for titanium alloys containing 0.05 to 10 per cent. niobium. The method is reasonably rapid. Six determinations can be finished in two days. The method should be applicable to many other materials besides titanium alloys.     

Extraktiv-photometrische Bestimmung von Titan in Aluminium und Aluminiumlegierungen mit 4,4′-Diantipyrylmethan

(DAPM). The use of DAPM as a spectrophotometric reagent for the determination of titanium in aluminium and aluminium alloys was investigated. To the solution, 0.5 N in hydrochloric acid, a 2% solution of DAPM in 0.5 N hydrochloric acid is added to form the yellow complex of titanium(IV) with DAPM. The addition of 20% solution of tin(II)chloride in 0.5 N hydrochloric acid yields a yellow precipitate, which is extracted by chloroform. The absorbance of the extract is measured at 390 nm. 0.01–0.1% of titanium have been determined in pure aluminium and Al-Mg-Zn alloys by the method suggested (standard deviation ±0.0004 to 0.0008%).     

Colorimetric and gravimetric determination of silicon in titanium and titanium alloys

Improved colorimetric and gravimetric methods are proposed for the determination of silicon in titanium and titanium alloys. In the colorimetric method the sample is dissolved in hydrofluoric acid. boric acid added and the; titanium oxidized with hydrogen peroxide and permanganate. The bulk of the titanium is precipitated as a crystalline precipitate by heating in boiling water, and the molybdenum color developed. A portion of the solution is filtered and the transmittance measured. In the gravimetric method the sample is fumed with milfuric acid. the silica ignited and fused with aodium carbonate, The silica is then dehydrated with perchloric acid. Thecolorimetric method is recommended for 0.003 to 1.5% silicon, and the gravimetric method for 0.3 to 5% silicon.     

A highly selective procedure for the spectrophotometric determination of aluminium with 8-hydroxy-quinoline and its application to the determination of

Aluminium, hydroxyquinolate can be quantitatively extracted by chloroform from an ammoniacal solution containing hydroxyquinoline, complexone and cyanide. Likewise extracted are titanium, vanadium, tantalum, niobium, uranium, zirconium, gallium, antimony, bismuth, indium and traces of beryllium. Aluminium can be separated from the first five elements by an extraction in ammoniacal solution containing hydrogen peroxide.Zirconium, gallium, bismuth and antimony can be eliminated by a cupferron extraction and indium by extraction with diethyldithiocarbamate. Beryllium is eliminated by performing an extraction with hydroxyquinoline at pH 5. The proposed method enables a practically specific photometrical determination of aluminium. Applications are given of the determination of trace and higher amounts of aluminium in steels, non-ferrous alloys and in glass.     

Determination of the types of nitrogen in steels containing aluminium or titanium by an extraction method with hydrogen

The extraction method with hydrogen, hitherto used to determine mobile nitrogen in steels over the temperature range 350–450°C, has been employed at higher temperatures to determine nitrogen bound as aluminium nitride, or as titanium nitride or carbonitride. In steels containing only silicon and titanium as deoxidizers, the nitrogen remaining after passage of hydrogen at 600 or 750°C is present as titanium nitride or carbonitride and can be determined by difference. In steels containing only silicon and aluminium as deoxidizers, the nitrogen remaining after passage of hydrogen at 600°C is present as aluminium nitride and can also be determined by difference. This was verified by determining the aluminium nitride indirectly. The nitrogen released from both the aluminium and titanium steels in hydrogen at 600°C probably results from dissociation of submicroscopic particles of manganese silicon nitride.     

Diffusion and permeability of aldehydes into blends of natural rubber and chemically modified low molecular weight natural rubber

Low molecular weight natural rubber (LMWNR) obtained from natural rubber (NR) by depolymerization of natural rubber latex (NRL) was modified by epoxidation to 35% epoxide level to yield epoxidized low molecular weight natural rubber (ELMWNR). The ELMWNR was in turn modified in a solution of thioglycollic acid (TGA) (0.5 mol phr) to yield a product of 20% conversion of its initial LMWNR epoxide. Blends of NR with LMWNR, ELMWNR and epoxidized low molecular weight natural rubber thioglycollic acid (ELWMNR‐TGA) adduct were made. The mixes were vulcanized at 150°C for 20 min before determining the system parameters (n and k), the sorption (S), diffusion (D) and permeability (P) of the vulcanizates in acetaldehyde and formaldehyde solutions at three different temperatures (25, 40 and 60°C) for a period of 90 days. The sorption, diffusion and permeability of the vulcanizates were found to be temperature dependent. The vulcanizates containing ELMWNR were found not to be easily penetrated by both acetaldehyde and formaldehyde when compared with base mix A that is vulcanizates with only NR. The reaction system was found not to be spontaneous but dependent on the activation energies. Copyright © 2005 John Wiley & Sons, Ltd.     

N-benzoyl-n-phenylhydroxylamine and the determination of titanium

Benzoylphenylhydroxylamine reacts with titanium in 10 N hydrochloric acid to give a ternary complex which, on extraction, permits the determination of 1–6 p.p.m. of titanium. Only niobium, in the presence of tin(II) chloride, is a serious interference. An enhanced sensitivity which is obtained if thiocyanate is present is advantageous if iron is absent. Titanium is accurately determined in steels, other alloys and refractories.     

The separation and determination of nickel, chromium, cobalt, iron, titanium, tungsten, molybdenum, niobium and tantalum in a high temperature alloy by anion-exchange

An anion-exchange method of separating the constituents in high temperature alloys has been devised. Nine elements including titanium, tungsten, molybdenum, niobium and tantalum are determined in an alloy on a single sample weight. Any combination of the elements mentioned above may be determined in steels and high temperature alloys with a simple ion-exchange scheme suitable for routine analysis.     

Determination of niobium in steels

The determination of niobium at levels of 0.01% and below is required in certain specifications for stainless-steel welding electrodes, containing 2-3% molybdenum and 0.01% titanium. A method has been developed, based on initial extraction of niobium thiocyanate into butyl acetate followed by stripping with fluoride and re-extraction of niobium thiocyanate after masking of the fluoride by addition of boric acid. The absorbance of the extract is measured at 385 nm. Mo, Ti, V and W can be tolerated at 50 times the concentration of Nb. For higher amounts of Mo, corrections can also be applied. Ta should, however, be restricted to ten times the Nb level. Precision and accuracy of the method are satisfactory. The time taken for an individual determination is about an hour. The method is applicable to mild, low-alloy, stainless and niobium-stabilized steels.     

Spectrophotometric determination of vanadium and its application to gas-turbine fuel-oils

A very sensitive spectrophotometric method for the determination of vanadium in furnace oils is described. The intense indigo-blue colour developed by the reaction of vanadium with tannin and thioglycollic acid is measured at a wavelength of 600 nm at pH 4 and obeys Beer's law between 0.5 and 5 ppm vanadium. The method is applicable to gas-turbine fuel-oil and special navy fuel-oils. The common mineral constituents usually present in such oils do not interfere.     

Polymerization of acrylonitrile. Kinetics of the reaction initiated by the vanadium(V)/thioglycollic acid redox system

The polymerization of acrylonitrile initiated by the vanadium(V)-thioglycollic acid redox system has been investigated in aqueous sulphuric acid under nitrogen over the range 30–45°. The polymerization is second order in monomer and first order in thioglycollic acid (TGA). The rate of vanadium(V) disappearance is proportional to (TGA) and [V(V)]. The effects of FeCl₃, CuSO₄ and acetic acid on the polymerization have been investigated. The proposed reaction scheme involves initiation by an organic free radical, produced by the interaction of V(V) with TGA and termination by V(V). Various rate parameters have been evaluated.     

Determination of boron in titanium alloys by means of ion exchange

There is need for a rapid method for the determination of moderate amounts of boron in titanium alloys. In this paper a method is proposed which uses ion exchange. The method is applicable to titanium alloys containing 0.025 to 1 per cent. boron. One or two grams of the sample are dissolved in hydrochloric acid, and the titanium and boron are oxidized with nitric acid. The bulk of the titanium is removed by a cation exchanger. A calcium carbonate separation is made to remove the residual titanium and adjust the acidity. The boron is then titrated with sodium hydroxide, after the addition of mannitol. None of the elements found in commercial titanium alloys interferes with the method.     

Extraction and spectrophotometric determination of titanium(IV) with malachite green and p-chloromandelic acid, with application to mild steels

A very sensitive, selective and simple method for extraction and spectrophotometric determination of titanium(IV) with an alpha-hydroxy acid has been developed. p-Chloromandelic acid reacts with titanium in weakly acidic aqueous solution at room temperature to form a complex anion extractable into chlorobenzene with Malachite Green as counter-ion. Titanium is determined indirectly by measuring the absorbance of Malachite Green in the extract at 630 nm. The calibration graph is linear for titanium(IV) over the range 0.25-7.5muM (0.05-1.44 mug); the apparent molar absorptivity is 1.31 x 10(5) l.mole(-1).cm(-1). The method has been successfully applied to the determination of titanium in mild steels.     

A new method for the direct precipitation of aluminium in the presence of iron

It is shown that aluminium can be precipitated as benzoate from solutions containing up to 1 gram of iron in the presence of thioglycollic acid, which reduces the iron and forms a soluble complex with ferrous iron. Very large amounts of such salts as ammonium chloride, sulphate and perchlorate, and sodium chloride do not interfere, nor do other divalent metals. Molybdates and tungstates are without effect, but chromium, vanadium and titanium interfere. This limits the direct application of the method in metallurgical analysis, but in many cases this speedy and complete separation will have many uses.     

银纳米颗粒的合成及其与曙红Y的相互作用

分别制备了以L-半胱氨酸(L-cyst.)或以巯基乙酸(TGA)保护的银纳米颗粒,并用紫外-可见分光光度法和透射电子显微技术(TEM)对两种不同状态的银纳米颗粒的结构作了表征。由其吸收光谱图显示,L-cyst.和TGA保护的银纳米颗粒的吸收峰依次位于384 nm和392 nm波长处;由TEM的检测结果表明:上述2种形态银纳米颗粒的粒度大小依次在10~40 nm和20~30 nm范围内。试验中发现,以L-cyst.保护的银纳米颗粒与曙红Y之间有明显的相互作用,导致其吸收峰从384 nm红移至395 nm;以TGA保护的银纳米颗粒与曙红Y之间未见有相互反应。初步探讨了其作用机理,认为系由于结合于银纳米颗粒表面的L-半胱氨酸分子所带的正电荷与曙红Y分子上的负电荷之间的静电作用的结果。