Titanium, analytical determination

Analytical and Test Methods. o-Nitrotoluene can be analyzed for purity and isomer content by infrared spectroscopy with an accuracy of about 1%. -Nitrotoluene content can be estimated by the decomposition of the isomeric toluene diazonium chlorides because the ortho and meta isomers decompose more readily than the para isomer. A colorimetric method for determining the content of the various isomers is based on the color which forms when the mononitrotoluenes are dissolved in sulfuric acid (45). From the absorption of the sulfuric acid solution at 436 and 305 nm, the ortho and para isomer content can be deterrnined, and the meta isomer can be obtained by difference. However, this and other colorimetric methods are subject to possible interferences from other aromatic nitro compounds. A titrimetric method, based on the reduction of the nitro group with titanium(III) sulfate or chloride, can be used to determine mononitrotoluenes (32). Chromatographic methods, eg, gas chromatography or high pressure Hquid chromatography, are well suited for the deterrnination of mononitrotoluenes as well as its individual isomers. Freezing points are used commonly as indicators of purity of the various isomers. 

Where the reduction potentials of two analytes are sufficiently different a mixture may be analysed. Titanium(III), = 0-lOV may be titrated with cerium(IV) in the presence of iron(II), =0.77 V usjng methylene blue as indicator. Subsequently the total, iron plus titanium, may be determined using ferroin as indicator. The determination of iron is illustrative of some practical problems which are encountered in direct titration procedures. 

The aluminum was determined spectrophotometrically using 8-hydroxy-quinoline in a known quantity of polymer obtained from the xylene solution and previously purified. The absence of titanium from the polymeric product, isolated in this fashion, was checked by conventional analytical methods. 

According to G. Pellagri,41 potassium chlorate inaq. soln. is reduced to the chloride by shaking it with iron filings and H. Eccles noted that it is readily reduced by boiling it with a copper-zinc couple—potassium perchlorate is not reduced under similar conditions. Hence, the amount of the one salt can be readily determined when in the presence of the other. On the other hand, J. G. Williams found the perchlorates are reduced by titanium trichloride, while the chlorates are not affected. Here again an analytical process is available. 

Major and minor elements in coal, having concentrations easily detectable by most modem analytical techniques, can be determined by a number of acceptable procedures. Various approaches, combining a. number of specific procedures, are frequently referenced in the literature. For example, the presently accepted procedure (ASTM D-2795) determines silicon, aluminum, iron, titanium, and phosphorus colorimetrically, calcium and magnesium chelatometrically, and sodium and potassium by flame photometry. This standard test method was withdrawn in 2001 but is still used in some laboratories. 

The analytical chemistry of titanium has been reviewed (179—181). Titanium ores can be dissolved by fusion with potassium pyrosulfate, followed by dissolution of the cooled melt in dilute sulfuric acid. For some ores, even if all of the titanium is dissolved, a small amount of residue may still remain. If a full analysis is required, the residue may be treated by moistening with sulfuric and hydrofluoric acids and evaporating, to remove silica, and then fused in a sodium carbonate—borate mixture. Alternatively, fusion in sodium carbonate—borate mixture can be used for ores and a boiling mixture of concentrated sulfuric acid and ammonium sulfate for titanium dioxide pigments. For trace-element determinations, the preferred method is dissolution in a mixture of hydrofluoric and hydrochloric acids. 

Obtaining realistic errors is one of the most difficult, yet most crucial problems in all flux estimates. Such errors can be approximated through an independent error analysis for several factors that are involved in estimating fresh and altered rock composition. There are uncertainties arising from petrographic observations, in the choices of representative samples, recovery rate biases, and analytical errors. In most cases analytical errors are a relatively minor source of uncertainty, and they are typically rather well documented. Probably the most crucial analytical uncertainty is in acurately determining the titanium concentration that is used as a normalizing factor to account for open-system behavior. This uncertainty directly relates to an error in the fluxes, and thus fluxes are difficult to constrain to better than 1 % of the whole rock abundance of a particular element. 

Other problems may be caused by the matrix of the sample itself. If chloride is present, a series of polyatomic chloride-containing species may cause major interferences. As an example, Ar CT is an intense peak that interferes with As". Arsenic is monoisotopic therefore appreciable levels of chloride in the sample will seriously compromise the precise determination of arsenic. Components of the sample matrix may also contribute to oxide formation. Oxides of the form MO give rise to peaks at the (M/Z)+16 position. One or more of these may interfere with nuclides of interest. An example of this is Ti 0 interfering with the analysis of Zn. The four other naturally occurring titanium isotopes would, of course, also give interference at their respective (M/Z)-i-16 values to any analytes with these masses. Formation of the oxide of the analyte also reduces the signal measured at M/Z. 

The size and distribution of pores and the size, distribution, and identity of minerals in coal specimens from an eastern Kentucky splint coal and the Illinois No. 6 coal seam were determined by means of transmission electron microscopy (TEM) and analytical electron microscopy (AEM). The observed porosity varies with the macerals such that the finest pores (<2-5 nm) are located in vitrinite, with a broad range of coarser porosity (40-500 nm) associated with the macerals exinite and inertinite. Elemental analyses, for elements of atomic number 11 or greater, in conjunction with selected area diffraction (SAD) experiments served to identify the source of the titanium observed in the granular material as the mineral rutile. Only sulfur could be de-tected in the other coal macerals. Dark-field microscopy is introduced as a means for determining the domain size of the coal macerals. This method should prove useful in the determination of the molecular structure of coal. 

When Lavoisier reformed chemistry in France, his work was being introduced in Germany by Martin Heinrich Klaproth (1743-1817). Trained as an apothecary, Klaproth taught himself the new chemical philosophy and became an assistant to Valentin Rose (1736-1771), one of the leading chemists of the day. He became director of Rose s pharmaceutical laboratory after Rose s death. Klaproth was an extremely good and extremely exact chemist, and a significant part of his work was directed at analytical chemistry, particularly the determination of characteristics of unknown compounds. During his years as director, he discovered or verified the discovery of zirconium, uranium, tellurium, and titanium. 

Other analytical problems to which the direct comparison method has been applied include the determination of mixed iron oxides in the oxide scale on steel [14.10], the beta phase in titanium alloys [14.11], and mixed uranium and plutonium carbides [14.12]. 

Another option is to place the filtration unit inside the flow cell, as demonstrated in the spectrophotometric flow injection determination of hydrogen peroxide [297]. The analyte interacted with titanium(IV) and 2-((5-bromopyridyl)azo)-5-(N-propyl-N-sulfopropylamino) phenol (PAPS) yielding a red-purple complex. After ion pairing with CTAB, the complex was adsorbed and concentrated on a very small area of the membrane filter positioned inside the flow cell. The analyte was quantified directly in the membrane by solid-phase spectrophotometry (see 4.1.1.4). Thereafter, ethanol was injected in order to solubilise the complex and transport it to waste. 

Arsonium salts have found considerable use in analytical chemistry. One such use involves the extraction of a metal complex in aqueous solution with tetraphenylarsonium chloride in an organic solvent. Titanium (TV) thiocyanate [35787-79-2] (157) and copper(II) thiocyanate [15192-76-4] (158) in hydrochloric acid solution have been extracted using tetraphenylarsonium chloride in chloroform solution in this manner, and the Ti(IV) and Cu(II) thiocyanates determined spectrophotometrically. Cobalt, palladium, tungsten, niobium, and molybdenum have been determined in a similar manner. In addition to their use for the determination of metals, anions such as perchlorate and perrhenate have been determined as arsonium salts. Tetraphenylarsonium permanganate is the only known insoluble salt of this anion. 

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