Normal thallium

Reported values for the normal thallium content of human body fluids and tissues are listed in Table 22.1. These data include only reliable results that were obtained using adequate analytical methods and with sufficient numbers of participants. The data may serve as reference values for unexposed individuals, and may also be used for environmental or toxicological diagnostic purposes. Background thallium concentrations in other human tissues may be classified only as indicative of T1 exposure liver <0.4 to 0.9 pgg dry weight (Johnson 1976), and feces < 0.02... 

Various values have been proposed as the upper limit of normal for the quantity of thallium in urine. Most published values for the upper limit of normal thallium concentration in urine are... 

Normally thallium, like mercury, is effectively removed by volatihsation in the sintering process. For direct smelting processes there may not be sufficient volatihsation with direct capture into the lead bulhon, and a direct method of separation may be required, as is the case at the Trail smelter with the introduction of the Kivcet process. In this case thallium is removed by the addition of zinc chloride to molten buUion, displacing thalhum as a thalhum chloride dross, and leaving zinc in the bullion for later removal. 

Tb allium, which does not occur naturaHy in normal tissue, is not essential to mammals but does accumulate in the human body. Levels as low as 0.5 mg/100 g of tissue suggest thallium intoxication. Based on industrial experience, 0.10 mg /m of thallium in air is considered safe for a 40-h work week (37). The lethal dose for humans is not definitely known, but 1 g of absorbed thallium is considered sufficient to kHl an adult and 10 mg/kg body weight has been fatal to children. In severe cases of poisoning, death does not occur earlier than 8—10 d but most frequently in 10—12 d. Tb allium excretion is slow and prolonged. For example, tb allium is present in the feces 35 d after exposure and persists in the urine for up to three months. 

When the reaction is run with potassium fert-butoxide in THF at -5°C, one obtains (after hydrolysis) the normal Knoevenagel product (32), except that the isocyano group has been hydrated (16-65). With the same base but with DME as solvent the product is the nitrile (33). When the ketone is treated with 31 and thallium(I) ethoxide in a 4 1 mixture of absolute ethanol and DME at room temperature, the product is a 4-ethoxy-2-oxazoline (34). Since 33 can be hydrolyzed to a carboxylic acid and 34 to an a-hydroxy aldehyde, this versatile reaction provides a means for achieving the conversion of RCOR to RCHR COOH, RCHR CN, or RCR (OH)CHO. The conversions to RCHR COOH and to RCHR CN have also been carried out with certain aldehydes (R = H). 

The thallium intermediates can be useful in directing substitution to specific positions when the site of thallation can be controlled in an advantageous way. The two principal means of control are chelation and the ability to effect thermal equilibration of arylthallium intermediates. Oxygen-containing groups normally direct thallation to the ortho position by a chelation effect. The thermodynamically favored position is... 

In another cohort study, no statistically significant clinical effects were found, even though urinary concentrations ranging up to 236pg/liter indicated exposures above the threshold limit value (TLV) of O.lmg/m A urine thallium concentration of lOOpg/1 corresponds approximately to a 40 hour/week exposure at O.lmg/m and normal values range between 0.6 and 2.0pg/l. ... 

Thiourea forms MX (thiourea) 4 compounds if the lattice energy of MX is iess than 160 Kcal/mole, so that M = K, Rb, or Cs. Other large cations form similar compounds, for example, thallium and lead. The structures consist of columns of cations surrounded by eight sulphur atoms at the comers of an approximately regular cube. Each sulphur atom is shared by two cations. The S—C bonds lie in planes normal to the column, and the NHg groups project into channels which contain the anion, and sometimes water molecules (34). 

Although there seems to be no doubt that Six William Crookes was the first to observe the green line of thallium, many chemical historians, especially the French ones, attribute the isolation of the metal itself to Claude-Auguste Lamy. He was bom on July 15, 1820, at Ndry in the Jura department of France, attended the ficole Normale Supdrieure in Paris, and at the age of thirty-one years received his doctorate from Lille, He taught physics, first at Limoges and later at Lille (16). 

One of the most famous applications in forensic science is the analysis of Napoleon s hair by ICP-MS after mineralization in concentrated nitric acid whereby an arsenic concentration about 40 times higher than normal (about 40p,gg 1) was measured (see Section 9.5). Ingested arsenic is known to be stored in sulfydryl rich tissue, like hair, nails or skin. ETV-ICP-MS combined with isotope dilution has been employed to measure thallium in human scalp hair from a person poisoned by thallium compared to control subjects, whereby several longitudinal concentration gradients for the analyzed segments (length 10 mm) were obtained.28... 

THALLIUM. [CAS 7440-28-0], Chemical element symbol Tl, at. no. 81, at. wt, 204,38, periodic table group 3. mp 303.5°C, bp 1447-1467°C, density 11.85 g/cm3 (20°C). Elemental thallium has a hexagonal close-packed crystal structure normally, but also exhibits a face-centered cubic crystal structure. 

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