Direct colorimetric determination of small amounts of tungsten in titanium

There is need for a rapid and accurate method for the determination of small amounts of tungsten in titanium. In this paper a direct colorimetric method is proposed for the determination of tungsten in titanium that is applicable to the range of 0.005 to 0.3 per cent. tungsten. The sample is dissolved in hydrochloric acid and the titanium and tungsten reduced with metallic zinc. Thiocyanate is added and the yellow color read at 410 millimicrons with a spectrophotometer. A study was made of the best conditions for developing the color, including the effect of varying amounts of titanium, thiocyanate and hydrochloric acid. An investigation was made to determine the proper wave length for reading the color, the stability of the color and effect of interferences.     

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.     

Colorimetric determination of tantalum in titanium alloys

Experimental work on tantalum-titanium alloys has been handicapped by the lack of accurate methods for the determination of the tantalum. In this paper a colorimetric procedure is proposed for the determination. The tantalum is separated completely from the titanium by two tannin precipitations with an intervening digestion with tannin. The tannin precipitate is ignited, fused with potassium bisulfate and the melt taken up with ammonium oxalate solution. Pyrogallol is then added and the intensity of the yellow color is measured. A study was made of the tantalum pyrogallol color to obtain optimum conditions. Elements that would be found in the usual tantalum-titanium alloys do not interfere with the method. More than 0.0025 gram of niobium interferes by cauaing occlusion of titanium by the tannin precipitate. This causes high results for tantalum, since titanium reacts with pyrogallol to produce a yellow color. The presence of more than 0.0050 gram of tungsten causes high results for tantalum because tungsten is partially precipitated by the tannin and reacts with pyrogallol to produce a yellow color. The proposed method is recommended for tantalum-titanium alloys containing 0.05 to 5 percent, tantalum.     

Colorimetric determination of chromium in titanium alloys

Chromium-titanium alloys are becoming increasingly important because of their strength and corrosion, resistance. Therefore, accurate methods for the determination of chromium in this type of alloy are needed. A colorimetric procedure for the determination of chromium in titanium alloys is proposed. In this method the chromium is oxidised to the chromate state by means of ammonium persulfate and potassium permanganate in the presence of silver nitrate as a catalyst. Diphenylcarbazide is then added to an aliquot of the solution, and the violet color read in 10 to 40 minutes at 580 millimicrons. None of the elements found in commercial titanium alloys, including iron, vanadium, molybdenum, and tungsten, interferes with the method. The proposed method is superior to the volumetric method for the determination of small amounts of chromium. The method is designed for titanium. alloys containing 0.02 to 4 per cent chromium.     

Colorimetric determination of iron in titanium alloys

There is need for an improved method for the determination of iron in titanium alloys. In this paper a colorimetric method using o-phenanthroline is proposed. The method is applicable to the range of 0.02 to 9 per cent. iron. Two modifications of a basic procedure are described. One modification, applicable to ordinary titanium alloys, is a direct method. A second modification, applicable to alloys containing large amounts of certain alloying elements, calls for a prior separation of the iron by an ether extraction. In a direct method a one gram sample is dissolved in hydrochloric acid and an aliquot of the solution taken. Hydroxylamine and ammonium tartrate are added, the pH of the solution is adjusted by the addition of sodium acetate, and o-phenanthroline added. A study was made to find the best pH and optimum amount of o-phenanthroline for the development of the color.     

A new colorimetric method for the determination of carbon disulphide and its application to the analysis of some dithiocarbamate fungicides

A new and convenient colorimetric method for determination of carbon disulphide, based on its transformation into bright yellow potassium benzyl trithiocarbonate through reaction with benzyl mercaptan and potassium hydroxide in tert.-butyl alcohol, has been successfully applied to determination of some dithiocarbamate fungicides in their formulations. The method possesses a distinct advantage in that it is free from all sources of errors/problems which are associated with the xanthate method for the analysis of these materials. The proposed method is precise and accurate and hence recommended for routine analysis of technical formulations containing dithiocarbamate fungicides.     

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.     

Determination of tin in titanium alloys

Tin-titanium alloys are becoming increasingly important; consequently a good method is needed for the determination of tin in this type of material. In this paper an accurate iodometric procedure is proposed for the determination. The sample is dissolved in sulfuric acid and the titanium oxidized with potassium permanganate. Tartaric acid is added and the tin precipitated with hydrogen, sulfide. The sulfide precipitate is dissolved in a mixture of sulfuric, perchloric and nitric acids and the solution evaporated to fumes of sulfuric acid. Water and hydrochloric acid are added, and the tin is reduced with lead and antimony trichloride and titrated with iodine. A study was made of the interfering elements that might be found in titanium alloys. The effect of antimony trichloride in reducing interference from copper was investigated. The method is recommended for titanium alloys containing 0.05 to 5.0 per cent. tin.     

Étude sur le dosage colorimétrique de l'aluminium dans les aciers

Colorimetric determination of aluminium by means of a new reagent, stilbazo, is studied.The investigation leads to a method for the direct determination of aluminiumsteel alloys: nitrided steels, magnetic steels.The aluminium is determined by a technique consisting of electrolysis with mercury cathode, separation of titanium and vanadium, if present, by chloroform extraction of the complexes of these elements with cupferron, and, finally, colorimetric determination.During these experimental investigations, observations have been made concerning the influence of a number of elements on the reaction of aluminium with stilbazo. The reactions of vanadium with various reagents (dicyandiamidine, diantipyrylphenylmethane, a-benzoinoxime) and the silico-vanado-tungstic complex have been studied.     

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.     

无线磁弹性免疫传感法测定水中痕量镉

基于抗原抗体特异性结合使镉附着在免疫传感器表面导致磁弹片共振频率降低的原理,建立了应用磁弹性免疫传感法测定水中痕量镉的方法。 其共振频率变化对应于磁弹性片表面附着物的质量变化。研究了聚乙烯亚胺用量、戊二醛用量、反应时间等因素对测定的影响。在最佳条件下,测定镉的线性范围为0.90~10.0 μg/L,检出限为为0.42 μg/L。 应用本方法测定了水样中的镉,测定结果与双硫腙比色法一致,回收率为96.5%~103.6%。     

A clinical assessment of direct electrochemical urate measurements

The response characteristics of various carbon substrates towards the direct oxidative measurement of urate and other key purine biomarkers have been compared. A novel carbon fibre laminate assembly has been proposed as an alternative substrate for the preparation of disposable sensing strips. The fabrication method is generic and readily transferable to a number of sensor applications. Its performance in the determination of urate within biofluids (serum and plasma) has been critically assessed. An inter-laboratory pilot study demonstrated the bioanalytical efficacy of the approach with the responses validated through comparison with the standard colorimetric (uricase/peroxidase) assay.     

Anodic stripping voltammetric determination of titanium(IV) using a carbon paste electrode modified with cetyltrimethylammonium bromide

A method is described for the voltammetric determination of titanium(IV) using a carbon paste electrode modified in situ with cetyltrimethylammonium bromide. The cationic micellar surfactant adsorbs onto the electrode particularly at negative potentials, simultaneously preconcentrating titanium(IV) as the oxalate complex with reduction to titanium(III). Anodic stripping voltammetry exploiting reoxidation can be used for the determination of trace levels of titanium(IV). Linearity between current and concentration exists between 5 and 160 mug l(-1) Ti(IV) (preconcentration time 2 min). The limit of detection (calculated as 3sigma) is 0.1 mug l(-1), with a preconcentration time of 10 min.     

An ultraviolet spectrophotometric method for the determination of small amounts of vanadium in ores and steel

The method proposed is suitable for a quick routine determination of small amounts of vanadium in certain ores and steel. The interference of chromium in the final determination of vanadium using the ultraviolet spectra was eliminated by the use of an ion-exchange resin. Reproduceability of results was found to be acceptable for a colorimetric method.     

Precise determination of boron in titanium by inductively coupled plasma mass spectrometry

A method was developed for the determination of boron in titanium by inductively coupled plasma mass spectrometry (ICP-MS). A commercially available PTFE sample introduction system, leading to the desired low detection limits for boron, was used. The method is suitable for the determination of boron concentrations down to about 1 μg g^?1 in the solid material. The influence of the internal standard on the precision was studied and beryllium was selected as the internal standard. For the titanium analysed (BCR reference material 090), the ICP-MS result agreed with those obtained using other techniques. Several bars of titanium reference material were supplied and a study of the homogeneity of boron in this material was made. Using analysis of variance on the results obtained for the different bars, the homogeneity of boron in the reference material could be estimated to be better than 2.1%.     

A permeation method for the determination of average concentrations of carbon monoxide in the atmosphere

A simple, inexpensive and reliable method for the determination of average concentrations of carbon monoxide in the atmosphere is described. Silver p-sulfa-moylbenzoic acid is used as the colorimetric reagent in a specially designed permeation device. The calibration graphs are linear up to 80 p.p.m. carbon monoxide, and the limit of detection is 2 p.p.m. for a 24-h exposure. Tests under field conditions are discussed.     

Polymerization with Fischer-Tropsch olefins – a new challenge in polymer science

Co- and ter-polymerization of ethylene with Fischer-Tropsch derived olefins having odd carbon number and branched olefins are investigated. A method of preparation of a robust, high productivity Ziegler-Natta catalyst suitable for ethylene co-polymerization with Fischer Tropsch olefin is reviewed. In supporting titanium tetrachloride, an attempt was made to control the titanium oxidation state. The resulting experimental data were fitted to a sub-sites model that associates titanium oxidation state with catalyst activity.     

New colorimetric method for the determination of nystatin

A new colorimetric method for the determination of nystatin is reported, based on the reaction of the alkaline hydrolysis product of nystatin with p-aminoacetophenone in presence of concentrated hydrochloric acid. The proposed method determines 0.2-1.0mg of nystatin with recovery of 100.7 +/- 1.2%. The method is adopted to the determination of nystatin in pharmaceutical preparations, and interference due to the presence of sugar is eliminated.     

Utilization of tetrazolium blue for the colorimetric assay of tannins in tea

A simple, rapid and accurate colorimetric method is proposed for the determination of tannins, based on the reduction of tetrazolium blue in alkaline medium by tannins at 90 ± 2 °C for 15 min, leading to the formation of a highly coloured formazan derivative. Absorbance measurements were made at 527 nm and the calibration graph was linear for 0.2-9.0 g/ml of tannic acid. For more accurate analysis, the Ringbom optimum concentration range was found to be 0.5–8.2 g/ml. The relative standard deviation for the determination in a tea sample containing 7.55% tannins was 1.65%. Most of the ingredients commonly found in tea samples do not interfere with the determination. Several tea samples were analysed using the proposed method.     

Rapid, selective, direct and derivative spectrophotometric determination of titanium with 2,4-dihydroxybenzaldehyde isonicotinoyl hydrazone

A simple and sensitive spectrophotometric method is developed for the determination of titanium in aqueous medium. The metal ion forms a reddish brown coloured complex with 2,4-dihydroxybenzaldehyde isonicotinoyl hydrazone (2,4-DHBINH) in the pH range 1-7. The complex shows two absorption maxima, one at 430 nm and the other at 500 nm. The reagent shows appreciable absorbance of 430 nm and negligible absorbance at 500 nm at pH 1.5. Beer's law is obeyed in the range 0.09 to 2.15 mug ml(-1) of titanium(IV). The molar absorptivity and the Sandell's sensitivity of the method are 1.35 x 10(4) 1 mol(-1) cm(-1) and 0.0049 mug cm(-2), respectively. A method for the determination of titanium by first-order derivative spectrophotometry is also proposed. The methods have been employed successfully for the determination of titanium in several alloy and steel samples.