Chlorine, elemental industrial preparation

Arsenic(III) chloride is an important starting material for synthetic inorganic and element-organic chemistry. Usually it is prepared by passing a chlorine gas stream over arsenic metal or by the reaction of arsenic(lll) oxide, disulfurdichloride, and chlorine gas. Industrially, arsenic(lll) chloride is obtained by the reaction of arsenic(III) oxide and hydrochloric acid. These methods are time consuming and complicated on a laboratory scale. 

C04-0145. Silicon tetrachloride is used in the electronics industry to make elemental silicon for computer chips. Silicon tetrachloride is prepared from silicon dioxide, carbon graphite, and chlorine gas. 

Figure 16.2a summarizes the major uses of chlorine. Chlorinated organic compounds, including 1,2-dichloro-ethene and vinyl chloride for the polymer industry, are hugely important. Dichlorine was widely used as a bleach in the paper and pulp industry, but environmental legislations have resulted in changes (Figure 16.2b). Chlorine dioxide, CIO2 (an elemental chlorine-free bleaching agent), is prepared from NaC103 and is favoured over CI2 because it does not produce toxic effluents. ...

Discussion The methods of preparing chlorine fall into four general classes, the electrolysis of a chloride, which is the chief industrial method, the oxidation of hydrochloric acid in which the oxygen from the oxidizing agent unites with the hydrogen of the acid and liberates the chlorine, the deeom-pO Sition of a hypochlorite, and the formation of a chloride which immediately breaks up into chlorine and another chloride containing less chlorine. The last of these methods is the one commonly used for the laboratory preparation of the element. 

X-ray fluorescence spectrometry This technique is extensively used in the industrial analysis of plastics for routine determination of traces of metals and nonmetal elements, i.e., iron, cobalt, nickel, chromium, copper, zinc, chlorine, bromine, titanium, aluminum, sodium, potassium, calcium, magnesium, vanadium, cadmium, and selenium. The main advantages are simple sample preparation and independence on the element state in chemical combination. 

Qualitative analysis requires that mixtures be separated into their components, which can be compounds or simple elements. Compounds, in turn, may be further separated into their constituent elements. In geology and the mining industry, for example, rocks, minerals, or soils are analyzed to find out what metals (such as copper, nickel, or titanium) or other elements (such as chlorine or phosphorus) are present. Municipal water faciUties have to identify and remove any contaminants (such as arsenic, lead, or nitrates) that might be present in surface or groundwater supplies before the water enters a city s water supply system. The food industry analyzes its products so that the labels can inform consumers of what kinds of fats, proteins, carbohydrates, vitamins, minerals, and fiber are present in canned, packaged, and prepared foods. The pharmaceutical industry analyzes samples of all of its products in the attempt to ensure against contamination. 

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