Vanadium, analytical methods metallic

The environmental scientist has at his disposal a variety of sensitive, multi-elemental analytical methods that can lead to a massive amount of data on airborne metals. Optimum use of these tools for environmental monitoring calls for focusing resources only on those metals that are environmentally important. Considerations of toxicity along with their ability to interact in the air, leading to the formation of secondary pollutants, and their presence in air have led to the identification of 17 environmentally important metals nickel, beryllium, cadmium, tin, antimony, lead, vanadium, mercury, selenium, arsenic, copper, iron, magnesium, manganese, titanium, chromium, and zinc. In addition to the airborne concentration, the particle size of environmentally important metals is perhaps the major consideration in assessing their importance. 

Nickel and vanadium along with iron and sodium (from the brine) are the major metallic constituents of crude oil. These metals can be determined by atomic absorption spectrophotometric methods (ASTM D-5863, IP 285, IP 288, IP 465), wavelength-dispersive X-ray fluorescence spectrometry (IP 433), and inductively coupled plasma emission spectrometry (ICPES). Several other analytical methods are available for the routine determination of trace elements in crude oU, some of which allow direct aspiration of the samples (diluted in a solvent) instead of time-consuming sample preparation procedures such as wet ashing (acid decomposition) or flame or dry ashing (removal of volatile/combustible constituents) (ASTM D-5863). Among the techniques used for trace element determinations are conductivity (IP 265), flameless and flame atomic absorption (AA) spectropho-... 

This book is a general survey of the nature of trace metals in petroleum and includes analytical methods for their determination. Vanadium, iron, nickel, cadmium, copper, and molybdenum— their nature, determination, chemical aspects, geochemistry, occurrence in new and used petroleum byproducts and their recovery for resource use—are dealt with in detail by the expert authors in this volume. Among the methods covered are instrumental analysis, neutron activation, activation analysis, oxidative demetallation and kinetic studies. Includes 54 figures and 60 tables. 

Analytical methods applied to estimate oxygen in alkali metals are the fast neutron activation for lithium oxide in lithium, vacuum distillation of excess alkali metal and analysis of the residue by atomic absorption spectrometry to estimate oxygen in sodium, as well as in the heavier alkali metals. Equilibration of oxygen between getters such as vanadium, liquid alkali metals and solid electrolyte oxygen meters, can be applied in several alkali metals. They measure oxygen activities directly in alkali metal circuits or closed containers. 

Much work on liquid metal velocity has been done with sodium and serves to illustrate its influence on corrosion. Bagnall and Jacobs [21] have attempted to unify the available data in the literature and correlate corrosion rate with temperature. Sodium velocity and oxygen were the two major variables taken into consideration. With oxygen interpreted on the vanadium wire equilibration scale, it was shown statistically that corrosion rate, R, was independent of velocity above about 3 m/s and directly proportional to oxygen concentration. An example of this correlation is shown in Fig. 4 where the variation of R with oxygen is plotted for type 316 stainless steel at 700°C. Data obtained at very low oxygen levels (<0.5 ppm by vanadium wire) deviate horn the predictive curve. At these low concentrations, mass loss appears to approach the model developed by Weeks and Isaacs [4]. Such behavior is not unreasonable since it is clear that mass loss will, in 2my event, not drop to zero at zero oxygen. Also, an approximate correlation between the vanadium wire scale and vacuum distillation values is shown on the abscissa. Note that the latter scale is not linear and that the vacuum distillation analytical method becomes insensitive below about 5 ppm. 

Samples Analyzed by Inductively Coupled Plasma (ICP) Metals — Where two or more of the following analytes are requested on the same filter, an ICP analysis may be conducted. However, the Industrial Hygienist should specify the metals of interest in the event samples cannot be analyzed by the ICP method. A computer print-out of the following 13 analytes may be typically reported Antimony, Beryllium, Cadmium, Chromium, Cobalt, Copper, Iron, Lead, Manganese, Molybdenum, Nickel, Vanadium, Zinc. Arsenic — Lead, cadmium, copper, and iron can be analyzed on the same filter with arsenic. 

In addition to ablation products such as nickel, copper, and iron now commonly present in exhaust, there is the potential occurrence in exhaust particulate of metals in use or considered for use as catalyst materials. Their detection would depend upon both increased use and/or increased analytical sensitivity. Efforts to quantify by routine methods emissions of platinum and palladium, now in widespread use in the oxidation catalyst, have failed to substantiate the presence of these metals in exhaust. An emission factor of 3.1 X 10" g/mile for platinum has been estimated (53). Other metals which have been considered for use in automotive catalysts include ruthenium and vanadium. 

The significant effect of traces of iron, nickel, copper and vanadium in petroleum feedstocks on processing economics has been responsible for the continuing attention focused on improvements in trace metal analytical procedures. This interest has intensified in our company because of the wide variety of crude oils now processed coupled with the need to meet more stringent contamination factors. These needs have increased demands on our laboratories for routine analyses at levels of less than 1 ppm. As a consequence our group was asked to evaluate requirements for trace metal analysis and to determine to what extent methods presently described in the literature could be adapted to our needs. 

Formation constants of 3d metal ions with A-m-tolyl-p-substituted benzohydroxamic acids and of rare earths with thenoylhydroxamic acid have been determined. Formation constants of proton and metal complexes of iV-phenyl-2-thenoyl- and A-p-tolyl-2-thenoyl-hydroxamic acids have also been determined. In addition, study has been made of the mixed ligand complexes involving nicotine- and isonicotino-hydroxamic acids. A method of extraction and spectrophotometric determination of vanadium with chlorophenylmethylbenzohydroxamic acid has also been published. It may be mentioned that hydroxamic acids (in particular, the A-phenylbenzohydroxamic acid) have been widely used as analytical reagents for metal ions. Solvent extraction of titanium by benzo- or salicyl-hydroxamic acid in the presence of trioctylamine in the form of coloured complexes has been reported. A-w-Tolyl-p-methoxybenzohydroxamic acid has been used for extraction and spectrophotometric determination of Mo and W from hydrochloric acid media containing thiocyanate. 

Information on the carbonyl chemistry of niobium and tantalum is, to date, very meager. The main difficulty appears to be the reduction of the usual pentavalent derivatives of these metals to the very low formal oxidation states of metal carbonyl derivatives. Nevertheless, the yellow anions [M(C0)6] (M = Nb, Ta) have been obtained by a method analogous to, but more difficult than, one of the preparations of the [VCCO) ]" anion. The method involves reduction of the pentachlorides with sodium metal in diglyme in the presence of high pressures of carbon monoxide (63). The niobium and tantalum derivatives are much more air-sensitive than the analogous vanadium derivative. The niobium derivative has not yet been obtained analytically pure (63). No chemistry of the [Nb(CO)J and the [Ta(CO)6] ions has been reported, even conversion to the neutral carbonyl derivatives [M(CO) (M = Nb or Ta = 1 or 2) or to the carbonyl hydride derivatives HM(CO)6 (M = Nb, Ta) still presenting unsolved problems. 

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