Thallium occurrence

ZiTKO V, Carson WV and Carson WG (1975) Thallium occurrence in the environment and toxicity to fish. Bull Environ Contam Toxicol 13 23-30. 

The usual symptoms in human thaHotoxicosis resulting from acute, subacute, or chronic intoxication are generaHy the same. Common symptoms include nausea, vomiting, abdominal coHc, pain in legs, nervousness and irtitabHity, chest pain, gingivitis or stomatitis, and anorexia. Alopecia (hair loss) does not always occur, especiaHy in cases of mass intake of thallium and low resistance where the patient may die before the occurrence of hair loss. 

The exhibition of variable valency is indeed a characteristic of transition metals. Main group metal ions such as those of groups 1 or 2 exhibit a single valence state. Other main group metals may show a number of valencies (usually two) which are related by a change in oxidation state of two units. This is typified by the occurrence of lead(iv) and lead(ii) or thallium(iii) and thallium(i). However, all the transition metals exhibit a range of valencies that is generally not limited in this manner. 

Exercise tolerance (stress) testing (ETT) is recommended for patients with an intermediate probability of CAD. Results correlate well with the likelihood of progressing to angina, occurrence of acute MI, and cardiovascular death. Ischemic ST-segment depression during ETT is an independent risk factor for cardiovascular events and mortality. Thallium myocardial perfusion scintigraphy may be used in conjunction with ETT to detect reversible and irreversible defects in blood flow to the myocardium. 

Occurrence. Thallium can be associated to heavy metals that occur in sulphidic ores (chalcophilic element behaviour) or to alkali metals in minerals such as car-nallite, sylvite, mica (the Tl+1 ion behaves as an alkali metal ion), or in true, but very rare, thallium minerals such as lorandite (T1AsS2), chalcothallite (Cu3T1S2). 

Very elegant experiments unequivocally proving the occurrence of electronic energy transfer were performed in 1922 and 1923 by Carlo and Franck [14], When a mixed vapor of mercury and thallium was irradiated with the mercury line at 253.67 nm, the emission lines of thallium could be observed in addition to the anticipated fluorescence spectrum of mercury. Since thallium cannot absorb 253.67-nm light, it must have been sensitized by the excited mercury atoms in order to produce the green fluorescence... 

Cyclopropane bonds are susceptible to oxidative cleavage (see Section 2.1.1.2.). Most of the oxidation reactions of activated cyclopropanes involve phenyl-substituted derivatives. When phenylcyclopropane was treated with lead(IV) acetate, 1,3-diacetoxy-l-phenylpropane (63%) and the elimination product cinnamyl acetate (32%) were obtained. The occurrence of traces of l,3-diacetoxy-2-phenylpropane could not be confirmed in later studies. The kinetics of the oxidation of various arylcyclopropanes with lead(IV) acetate, thallium(III) acetate and mercury(II) acetate have been studied. 4-Methoxyphenyl, 4-tolyl, and 4-chlorophenyl derivatives and their meta analogs were treated with these reagents and the rates of reaction and product distributions analyzed. Using lead(IV) acetate, diacetates 1 and cinnamyl acetates 2 were obtained in ratios of about 4 1, whereas thalhum(III) acetate gave the diacetates almost exclusively (see following table). ... 

After many years of laboratory experience with various azides, the authors can report no occurrence of poisoning symptoms attributable directly to solid azides. However, with substances such as thallous azide, the physiological effects of thallium, in addition to the azide toxicity, are of equal concern. 

Information is provided on the occurrence, environmental fate, available analytical methods, and treatment techniques foraldrin, ammonia, antimony, beryllium, boron, chlorpyrifos, isophorone, malathion, p-nitrophenol, phenol, silver, and thallium. 

Thallium is a rare element which occurs in the Earth s crust at an estimated abundance of 0.1 to 0.5 ligg (see Part I, Chapter 1). The specific ionic properties of thallium (e.g., ionic radius Tl 0.147 nm) are similar to those of potassium and rubidium (ionic radius K 0.133 nm, Rb" 0.147 nm) thus, thallium occurs ubiquitously as a trace element within the environment, mainly in association with K and Rb. Besides its occurrence in widespread potassium compounds, thallium is a trace component in iron, zinc, copper, and lead minerals (Nriagu 1998). 

In contrast to the occurrence of thallium as trace element, thallium minerals are very rare. Crookesite (from Skrikerum/ Sweden) is a mixture of the selenides of copper, thallium, and silver. Similar chemical compositions have been found in berze-lianite (Germany) and lorandite (Macedonia). Thallium has also been found in extraterrestrial material meteoric stones contain 0.001 to 0.2 tgg whilst lunar minerals contain 0.0006 to 0.0024 pgg (Urey 1952, Wedepohl 1974). 

In contrast to the small world production of thallium of about 10-15 tons per year, the annual amount of thallium in waste material is estimated to be about 600 tons (Micke et al. 1983). The main anthropogenic occurrence of thallium in the environment results from emissions of the highly volatile metal and its compounds from some industrial processes for example, the smelting of chalcogenic ores - especially lead and zinc sulfides - yields thallium emissions. 

In addition to the exciton band, energy states may be created between valence and conduction bands because of crystal imperfections or impurities. Particularly important are the states created by the activator atoms such as thallium. The activator atom may exist in the ground state or in one of its excited states. Elevation to an excited state may be the result of a photon absorption, or of the capture of tm exciton, or of the successive capture of an electron and a hole. The transition of the impurity atom from the excited to the ground state, if allowed, results in the emission of a photon in times of the order of 10" s. If this photon has a wavelength in the visible part of the electromagnetic spectrum, it contributes to a scintillation. Thus, production of a scintillation is the result of the occurrence of these events ... 

There are two stable isotopes 203-TI (29.52% nat. occurrence) and 205-TI (70.48% nat. occurrence). Thallium can occur in the zero-, mono- and trivalent state. The element is easily oxidized and of no pronounced technical use. 

Range of occurrence of thallium (nonanthropogenically polluted areas)... 

For thallium, determinations at the 276.78 nm line with an acetylene/air flame are used throughout. Matrix problems are very low, but the sensitivity with regard to the low level of occurrence is poor. The sensitivity can be increased by mounting a slotted quartz tube on the burner head STAT = "slotted tube atom trap") (Milner, 1983), which leads to a detection limit of about 20 mg/kg in the solid sample, which is insufficient for the analysis of biological matrices. In MIBK extracts, determination of thallium is much more sensitive in flame AAS than in aqueous solutions (till about 7-fold). This can be used for solvent extraction of thallium from 0.1M HBr (Hubert and Chao, 1985), as xanthate at pH 8 (Aihara and Kiboku, 1980), or as iodide with tri-n-octylphosphinoxide into MIBK, and direct aspiration of the organic phase into the flame. 

The occurrence of an oxidation state two below the group valence is due to what is commonly called the inert pair effect . The term refers to the resistance of a pair of s-orbit electrons to participate in bond formation [1]. Thallium regularly forms the monovalent oxidation state rather... 

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