Antimony-free effect

At the end of the twentieth century, maintenance-free VRLA batteries were invented. The first VRLA batteries employed lead—calcium grids. The antimony-free effect exhibited fully, which forced metallurgists to switch back to Pb—Sb alloys for the positive grids, minimising... 

The properties of the corrosion layer, and of its interfaces, depend strongly on the additives to the grid alloy (in this case, antimony). Antimony affects the corrosion layer in such a way that it does not limit the discharge of the active mass, so the latter exhibits its full capacity. This phenomenon is known as antimony-free effect . 

The effect of a particular element on the odour of its compound seems also to lend support to the residual affinity theory, for it is only the elements which possess residual affinity in certain of their compounds, which function as osmophores. Oxygen, nitrogen, sulphur, phosphorous, halogens, arsenic, antimony, bismuth, etc., whose valencies vary under certain conditions are powerfully osmophoric whereas carbon, hydrogen, and many others which have a constant valency are practically non-osmophoric, and it is very instructive to note that the element is osmophoric when it is not employing its full number of valencies and therefore has free affinity. 

The reaction is a sensitive one, but is subject to a number of interferences. The solution must be free from large amounts of lead, thallium (I), copper, tin, arsenic, antimony, gold, silver, platinum, and palladium, and from elements in sufficient quantity to colour the solution, e.g. nickel. Metals giving insoluble iodides must be absent, or present in amounts not yielding a precipitate. Substances which liberate iodine from potassium iodide interfere, for example iron(III) the latter should be reduced with sulphurous acid and the excess of gas boiled off, or by a 30 per cent solution of hypophosphorous acid. Chloride ion reduces the intensity of the bismuth colour. Separation of bismuth from copper can be effected by extraction of the bismuth as dithizonate by treatment in ammoniacal potassium cyanide solution with a 0.1 per cent solution of dithizone in chloroform if lead is present, shaking of the chloroform solution of lead and bismuth dithizonates with a buffer solution of pH 3.4 results in the lead alone passing into the aqueous phase. The bismuth complex is soluble in a pentan-l-ol-ethyl acetate mixture, and this fact can be utilised for the determination in the presence of coloured ions, such as nickel, cobalt, chromium, and uranium. 

A number of objections have been raised to the use of the term. In the first place, the list of so-called heavy metals usually includes some elements that are not even metals, such as the semimetals arsenic and antimony. Also, some of the "heavy metals" are not really very "heavy" by almost any standard. Beryllium, for example, has an atomic mass of about 9, and aluminum, an atomic mass of about 27. Yet both are often classified as "heavy metals." For these reasons, some authorities now prefer the term toxic metals to the more traditional term heavy metals. Either term can refer to elements in both their free and combined states. The table on pages 120-121 provides an overview of the sources and health effects of some heavy metals,... 

Antimony-doped SnOi films were deposited by adding SbCls to the deposition solution. Sb is a well-known n-type dopant used to increase the conductivity of SnOi films. The Sb concentration in the films increased hnearly with that in the deposition solution and was somewhat less than the solution concentration (e.g., 6% Sb in solution gave ca. 4% in the film). The Sb doping increased both the visible/near-lR transmission and mid-lR reflectance of the films, compared to the undoped films. These spectra are similar to those for doped ZnO (Fig. 7.3), and the effect of doping can be explained in the same way. The bandgap increased to 4.1 eV, compared to 3.56 eV for the undoped film, explained through band filhng by free electrons. 

The next test involved the distribution of lead in FDR between two solvents, namely, petroleum ether and water, in an attempt to determine the effect of water on the level of lead in FDR lead was chosen because it is present in FDR at a much higher level than either antimony or barium. Separation funnels on a vibration-free surface were used for the test. Before use, both the petroleum ether and deionized water were analyzed for lead with negative result. The results are given in Table 20.5. 

The nylon-coated bullets from Smith Wesson and the Geco TMJ bul-let/new primer composition, although effective in markedly reducing the lead levels, did not totally eliminate the problem. In 1983, Dynamit Nobel introduced 9 mmP caliber ammunition with a TMJ bullet and a primer free of lead, antimony, barium. The new primer type was called Sintox. A typical Sintox primer composition contains 15% diazodinitrophenol (DDNP) and 3% tetracene as the explosive ingredients, 50% zinc peroxide as the oxidizer, 5% of 40-pm size titanium metal powder, and 27% nitrocellulose as propellant powder.202 As expected, other munitions manufacturers eventually introduced similar ammunition, some with primers that were lead free but containing antimony and barium and others free of lead, antimony, and barium. The objective was to produce ammunition which performed satisfactorily in every way and did not produce any toxic product on discharge. 

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