Arsenicals, antimonials, and mercurials

2 Cephalosporins, bacitracin, and other inhibitors of the formation of new walls. 453 

Although the majority of biologically active substances combine only loosely with receptors and are easily released by washing, a few agents combine by covalent bonds which are of a more durable character (see Section 8.0). Covalent bonds involving carbon can be broken by great heat and also by powerful chemicals, but few can be ruptured by mild reagents at temperatures compatible with life. 

Although Ehrlich had found that pentavalent arsenicals did not act in the body until reduced to arsenoxides5 it had not occurred to him that arsenobenzenes acted only after oxidation to arsenoxides. This was established between 1920 and 1925 by Swiss-born Carl Voegtlin and his co-workers in the United States Public Health Service (for a review5 see Voegtlin5 1925)- 

1 The parasiticidal effect in trypanosome-infected rats of (A) arsphen-amine ( Salvarsan ), (B) oxophenarsine ( Mapharside ), and (C) oxo-phenarsine plus reduced glutathione. (Redrawn from Voegtlin, 1925.) 

The reaction of arsenoxides with thiol-groups is reversible, and parasites that have been treated with several lethal doses of arsenic can be saved if subsequently treated with many equivalents of a thiol-compound. 

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Sakamoto, H., Kamada, M. Yonehara, N. 1988. The contents and distributions of arsenic, antimony, and mercury in geothermal waters. Bulletin of the Chemcal Society of Japan, 61, 3471-3477. 

The one exception is the capacity of some micro-organisms to methylate certain metals, e.g. arsenic, antimony and mercury, probably as a kind of detoxification mechanism. Methylcobal-amin is the only organometallic compound known to have a physiological function in life processes. 

Stroh, A., andVollkopf, U. (1993). Optimization and use of flow injection vapour generation inductively coupled plasma mass spectrometry for the determination of arsenic, antimony and mercury in water and sea-water at ultratrace levels. J. Anal. At. Spectrom. 8(1), 35-40. 

The principal constituents of the paniculate matter are lead/zinc and iron oxides, but oxides of metals such as arsenic, antimony, cadmium, copper, and mercury are also present, along with metallic sulfates. Dust from raw materials handling contains metals, mainly in sulfidic form, although chlorides, fluorides, and metals in other chemical forms may be present. Off-gases contain fine dust panicles and volatile impurities such as arsenic, fluorine, and mercury. 

Potassium, sodium, magnesium, and mercury can be distilled over niobium without formation of alloys arsenic, antimony, and tellurium do not form alloys below 500° to 600° C. 

Weiss, H.V. and Bertine, K.K. (1973) Simultaneous determination of manganese, copper, arsenic, cadmium, antimony and mercury in glacial ice by radioactivation. Analytica Chimica Acta, 65(2), 253-59. 

Methods for several metals or metalloids involve conversion to a volatile form. Arsenic, antimony, and selenium can be reduced to their volatile hydrides, AsH3, SbH3, and H2Se, repectively, which can be determined by atomic absorption or other means. Mercury is reduced to volatile mercury metal, which is evolved from solution and measured by cold vapor atomic absorption. 

A. Qualitative Analysis.—Several methods may be employed for the qualitative determination of the platinum metals. The procedure is necessarily varied somewhat according to the nature and number of other metals present. These frequently comprise gold, mercury, arsenic, antimony, and tin. 

Chemical Reactions.—The iodine can be replaced by chlorine, using either the gas itself or chlorides, such as those of mercuric mercury, arsenic, antimony and tin. A sulphoiodide is formed when the triiodide is heated with the trisulphide —... 

Recommended conditions for flame and approximate values for ETA (graphite rod, etc.) atomizers are given in Table 2 for a number of elements important with regard to air pollution studies. Conditions are included in the table for the flame system used when hydrides of arsenic, antimony and selenium are generated and passed through the flame. Burrel [16] discusses generation of metal hydrides and cold-vapor mercury evolution techniques in great detail. 

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