Arsenic compound

Arsenic is the third member of the nitrogen family of elements and hence possesses an outermost shell having the electron configuration of 4 The 

Arsenic compounds have numerous practical appHcations. Although a variety of inorganic and organic arsenicals are used in commerce, arsenic trioxide [1327-53-3] AS2O2, accounted for 98% of the arsenic consumed in 1988 (2). 

The commercial uses of arsenic compounds in 1988, measured in terms of elemental arsenic, are wood (qv) preservatives, 69% agricultural products (herbicides (qv) and desiccants (qv)), 23% glass (qv), 4% nonferrous alloys and electronics, 2% and animal feed additives and pharmaceuticals (qv), 2% (see Feeds AND feed additives). Chromated copper arsenate (CCA) [11125-95-4] is the most widely used arsenic-based wood preservative. The Environmental Protection Agency has, however, restricted the use of arsenical wood preservatives to certified appHcators. 

The principal sources of imported arsenicals by the United States for the years 1986, 1987, and 1988 are shown in Table 1. 

Others includes Belgium-Luxembourg, China, Hong Kong, Japan, Philippines, South Africa, and Germany. 

The primary world producers of arsenic trioxide for 1988 were Chile, 7,000 t France, 10,000 t Sweden, 10,000 t and Russia, 8,100 t. The December 31, 1988 total world production capacity was 70,000 t. The price of arsenic trioxide (95% pure) in 1986 was 0.726/kg, fob, Tacoma, Washington the price of Mexican, 99.13% arsenic trioxide in 1986 and 1987 was 0.968/kg, fob, Laredo, Texas. 

Arsenic compounds must be considered extremely poisonous. Dust or fumes irritate mucous membranes and lead to arsenical poisoning. When swallowed they irritate the stomach and affect the heart, liver, and kidneys. Nervousness, thirst, vomiting, diarrhea, cyanosis, and collapse are among the symptoms of arsenical poisoning (3). In spite of the toxicity of arsenic compounds, there is evidence that arsenic is an essential nutrient for several animal species (4). 

The poisonous effect of arsenic has been known since ancient times and its application against insects was recommended as early as the seventeenth century in a book by John Worlidge (Munro, 1946). The use of various inorganic preparations for plant protection increased to several hundred million tons per year by the 1940s, but since then they have been replaced to a considerable extent by chlorinated hydrocarbon insecticides. 

Smith (1907) recommended the use of calcium arsenate instead of lead arsenate. Of the calcium salts of arsenic acid, mainly the acid salt of structure 3, and to a lesser extent the neutral salt of structure 4 and the basic salt of structure 5, have been applied in protection against insect pests in orchards, cotton and other plants. 

Roark (1942) prepared several modifications of Paris green in which the acetate radical was exchanged for other organic acid radicals. Of these, the oleate and stearate analogues, owing to their lipophilic character, were readily miscible with preparations of oily spray-type compounds. However, they did not find wide practical application. 

The experiments of Yun Fan (1947) were similarly aimed at the enhancement of lipid solubility. In these experiments, the insecticidal action of phenylarsonic acid and its derivatives substituted in the ring was investigated. Of this type of insecticide OT-chlorophenylarsonic acid (6) proved to be the most efficient. 

Preparations containing arsenic cannot strictly be considered as insecticides, as they are more or less toxic to all living organisms. In fact they had also been used as raticides and fungicides. Their use has been decreased owing to continuing improvements in human hygiene and environmental protection. 

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M.p. — 116-3 C, b.p. —55°C. An unstable poisonous gas (metal arsenide plus acid or arsenic compounds plus Zn plus dil. acid, AsCla plus LiAlH4) which decomposes to As... 

Basic copper ethanoate arsenates(iii) prepared from verdigris (or other basic copper salt), sodium arsenate(m) and ethanoic acid. Used in insecticides for spraying fruit trees. Readily decomposed to soluble arsenic compounds so use is very restricted. 

As can be expected, antimony compounds resemble those of arsenic. In the Marsh test, antimony compounds again give a black deposit which, unlike that formed by arsenic compounds, is insoluble in sodium chloratefi) solution. 

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