Bismuth traces

Fig. 4.8 FIA assembly for continuous generation of hydrides and transport to the quartz cell of the atomic absorption spectrometer, designed for the determination of bismuth traces. (Reproduced from [4] with permission of the American Chemical Society).

Crude lead contains traces of a number of metals. The desilvering of lead is considered later under silver (Chapter 14). Other metallic impurities are removed by remelting under controlled conditions when arsenic and antimony form a scum of lead(II) arsenate and antimonate on the surface while copper forms an infusible alloy which also takes up any sulphur, and also appears on the surface. The removal of bismuth, a valuable by-product, from lead is accomplished by making the crude lead the anode in an electrolytic bath consisting of a solution of lead in fluorosilicic acid. Gelatin is added so that a smooth coherent deposit of lead is obtained on the pure lead cathode when the current is passed. The impurities here (i.e. all other metals) form a sludge in the electrolytic bath and are not deposited on the cathode. 

This is a radioactive element. It occurs in minute traces in barium and thorium minerals, but it can be produced by irradiation of bismuth in a nuclear reactor. (The study of its chemistry presents great difficulty because of its intense a radiation). 

Bismuth concentrates in the dorn until the last stages of cupeUation, when it is oxidized and removed with the Htharge. After the last Htharge has been removed, it is often necessary to add bars of refined lead to provide more Htharge to carry off the last traces of bismuth. The dorn metal is then cast into bars for marketing. 

Some elements found in body tissues have no apparent physiological role, but have not been shown to be toxic. Examples are mbidium, strontium, titanium, niobium, germanium, and lanthanum. Other elements are toxic when found in greater than trace amounts, and sometimes in trace amounts. These latter elements include arsenic, mercury, lead, cadmium, silver, zirconium, beryUium, and thallium. Numerous other elements are used in medicine in nonnutrient roles. These include lithium, bismuth, antimony, bromine, platinum, and gold (Eig. 1). The interactions of mineral nutrients with... 

Solders are alloys that have melting temperatures below 300°C, formed from elements such as tin, lead, antimony, bismuth, and cadmium. Tin—lead solders are commonly used for electronic appHcations, showing traces of other elements that can tailor the solder properties for specific appHcations. 

Refining. The alloy of bismuth and lead from the separation procedures is treated with molten caustic soda to remove traces of such acidic elements as arsenic and teUutium (4). It is then subjected to the Parkes desilverization process to remove the silver and gold present. This process is also used to remove these elements from lead. 

For the deterrnination of trace amounts of bismuth, atomic absorption spectrometry is probably the most sensitive method. A procedure involving the generation of bismuthine by the use of sodium borohydride followed by flameless atomic absorption spectrometry has been described (6). The sensitivity of this method is given as 10 pg/0.0044M, where M is an absorbance unit the precision is 6.7% for 25 pg of bismuth. The low neutron cross section of bismuth virtually rules out any deterrnination of bismuth based on neutron absorption or neutron activation. 

Cobalt is the thirtieth most abundant element on earth and comprises approximately 0.0025% of the earth s cmst (3). It occurs in mineral form as arsenides, sulfides, and oxides trace amounts are also found in other minerals of nickel and iron as substitute ions (4). Cobalt minerals are commonly associated with ores of nickel, iron, silver, bismuth, copper, manganese, antimony, and 2iac. Table 1 Hsts the principal cobalt minerals and some corresponding properties. A complete listing of cobalt minerals is given ia Reference 4. 

Emissions from other nonferrous metal facilities are primarily metal fumes or metal oxides of extremely small diameter. Zinc oxide fumes vary from 0.03 to 0.3 jiim and are toxic. Lead and lead oxide fumes are extremely toxic and have been extensively studied. Arsenic, cadmium, bismuth, and other trace metals can be emitted from many metallurgical processes. 

Refining operations have two principal wastestreams, waste electrolyte and cathode and anode washwater. Spent electrolyte is normally recycled. A bleed stream is treated to reduce copper and impurity concentration. Varying degrees of treatment are necessary because of the differences in the anode copper. Anode impurities, including nickel, arsenic, and traces of antimony and bismuth, may be present in the effluent if the spent electrolyte bleed stream is discharged. Tables 3.14 and 3.15 present classical and toxic pollutant data for raw wastewater in this subcategory. 

Also contains antimony (about 8%). cAlso contains bismuth (about 6%). Also contains traces of gold. 

Nakashima et al. [719] detail a procedure for preliminary concentration of 16 elements from coastal waters and deep seawater, based on their reductive precipitation by sodium tetrahydroborate, prior to determination by graphite-furnace AAS. Results obtained on two reference materials are tabulated. This was a simple, rapid, and accurate technique for determination of a wide range of trace elements, including hydride-forming elements such as arsenic, selenium, tin, bismuth, antimony, and tellurium. The advantages of this procedure over other methods are indicated. 

Berndt et al. [740] have shown that traces of bismuth, cadmium, copper, cobalt, indium, nickel, lead, thallium, and zinc could be separated from samples of seawater, mineral water, and drinking water by complexation with the ammonium salt of pyrrolidine- 1-dithiocarboxylic acid, followed by filtration through a filter covered with a layer of active carbon. Sample volumes could range from 100 ml to 10 litres. The elements were dissolved in nitric acid and then determined by atomic absorption or inductively coupled plasma optical emission spectrometry. 

Tseng et al. [69] determined 60cobalt in seawater by successive extractions with tris(pyrrolidine dithiocarbamate) bismuth (III) and ammonium pyrrolidine dithiocarbamate and back-extraction with bismuth (III). Filtered seawater adjusted to pH 1.0-1.5 was extracted with chloroform and 0.01 M tris(pyrrolidine dithiocarbamate) bismuth (III) to remove certain metallic contaminants. The aqueous residue was adjusted to pH 4.5 and re-extracted with chloroform and 2% ammonium pyrrolidine thiocarbamate, to remove cobalt. Back-extraction with bismuth (III) solution removed further trace elements. The organic phase was dried under infrared and counted in a ger-manium/lithium detector coupled to a 4096 channel pulse height analyser. Indicated recovery was 96%, and the analysis time excluding counting was 50-min per sample. 

The delayed light emission as observed from the Bolonian stone is now classified as phosphorescence. We know now that these stones contain barium sulfate with traces of bismuth and manganese, and that the corresponding reducing process concerns the transformation of sulfate into sulfur. It is now well known that alkaline earth metal sulfates emit phosphorescence that strongly increases when traces of heavy metals are present. The so-called inorganic multi-component compounds phosphor and crystallophosphor are in fact polycrystalline substances containing traces of some ionic activators of luminescence. 

Owing to the toxicity of mercury and its disposal problem, solid electrodes are now very popular. In particular, electrodes made of carbon such as glassy carbon, graphite, carbon paste, and carbon fibers have gained popularity. Mercury, gold, bismuth, and other metals can be deposited as thin metal films on carbon and serves as thin metal film electrodes (TMFE) with excellent analytical advantages in trace metal analysis. The choice of working electrode is determined by the redox... 

Thin foils rather than wires were used in the two following investigations. The 7S of zirconium at a temperature near the melting point appeared65 to be 1850 240 dyn/cm. For a copper containing traces of bismuth, 7S = 1350 erg/cm2 was found66. ... 

Polonium is found only in trace amounts in the Earths crust. In nature it is found in pitchblende (uranium ore) as a decay product of uranium. Because it is so scarce, it is usually artificially produced by bombarding bismuth-209 with neutrons in a nuclear (atomic) reactor, resulting in bismuth-210, which has a half-hfe of five days. Bi-210 subsequently decays into Po-210 through beta decay The reaction for this process is Bi( ) Bi — °Po + (3-. Only small commercial milligram amounts are produced by this procedure. 

Tin obtained above contains small amounts of impurities. It is purified by resmelting in a small reverberatory furnace at a temperature just above the melting point of tin. The molten tin is drawn out, separating iron, copper, arsenic, antimony, and other metals. Purified tin is further refined by boiling or polling processes to remove traces of impurity metals, such as lead and bismuth. 

In the last decade, most of the contributions to the chemistry of polonium have, rather naturally, been made by workers employed in the Atomic Energy Establishments of the United Kingdom and the United States, where milligram amounts of the element have been extracted from irradiated bismuth. Before this, all the experimental work on the element had been on the trace scale, in which quantities from 10 10 to 10 6 g were used, apart from one large source, of about 100 Mg of polonium mixed with... 

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