Chromium arsenates

The results of one research programme indicate that copper-chromium-arsenic treatments are not corrosive towards galvanised steel and stainless steel in the moisture content range 15-22%. 

Yeates, G.W., V.A. Orchard, T.W. Speir, J.L. Hunt, andM.C.C. Hermans. 1994. Impact of pasture contamination by copper, chromium, arsenic timber preservative on soil biological activity. Biol. Fertil. Soils 18 200-208. 

Chromium Arsenates.—Chromic Orthoarsenate, CrAs04, is formed as an apple-green precipitate when potassium dihydrogen orthoarsenate is added to a solution of a chromic salt.11... 

McCarthy and coworkers (74) at the Australian Forest Products Laboratory reported that a pressure treatment for pine posts with zinc-copper-chromium-arsenic-phosphorus preservative produced a leach-resistant treatment having both fire retardancy and preservation against decay. This treatment system is reported to have commercial application in Australia. 

Metals are major pollutants only at wood preserving plants that treat with water-borne salts of copper, chromium, arsenic, and zinc. 

Metallic potassium and sodium are explosively converted into the hydroxides when brought into contact with concentrated solutions of hydrogen peroxide many of the heavier metals such as zinc and iron, and especially aluminium,3 are readily changed into their respective hydroxides, whilst chromium, arsenic, and molybdenum are oxidised respectively to chromic, arsenic, and molybdic acids. Colloidal tellurium yields telluric acid with very dilute solutions of peroxide4 the crystalline modification reacts slowly with 60 per cent, peroxide at 100° C. 

British Standard 5666, Methods of Analysis of Wood Preservatives and Treated Timber, Part 3, Quantitative Analysis of Preservatives and Treated Timber Containing Copper, Chromium, Arsenic Formulations, British Standards Institution, 2 Park Street, London W1A 2BS, 1979. 

AszCrjOa (s) 3CrO AS2O5 (s) Chromium Arsenate As2Cr30g (s) 3CrO AS2O5 (s)... 

Mercury, arsenic and cadmium are metals, which are volatile at low tenq>eratures (356.88, 614 and 767 °C respectively). Such metals must be captured at the exit of the gas after the condensation columns. Arsenic appears in treatments like CCA. It was shown that CCA (Copper, Chromium, Arsenic) treated wood could be pyrolysed with a negligible release of copper and chromium and a minimal release of arsenic (76,84 % of arsenic was found in the pyrolysis residues) at a reactor tenq)erature of 350 °C during 20 minutes, using a nitrogen at a flow rate of 5 Nm /h. [5]... 

Figure 6 shows that the increase in zinc and copper content in the charcoal is due to their concentration in this product. The pyrolytic liquids content in these two metals is very variable. But the majority of zinc and copper is found in the charcoal as well as for nickel, lead and chromium. The same conclusion was observed for CCB (Copper, Chromium, Arsenic) treated wood [2]. 

Thermogravi metric analysis (TGA) of CCA treated wood and the major arsenic compound in CCA treated wood (chromium arsenate (CrAs04)),... 

Based on the TG study of hydrated chromium(III) arsenate, which is the major arsenic compound in CCA treated wood, and on the results of equilibrium calculations carried out by other researchers [18, 19, 20], it is concluded that the decomposition of hydrated chromium arsenate results in the formation of solid Cr Oj and gaseous H7O, Ojand As Oft, according to the scheme ... 

Many of the biocides presently used in wood preservation preparations, e.g. pentachlorophenol (PCP), linane (y-HCH), creosote, and copper chromium arsenic-salts... 

McCarthy et al. (97) tested a zinc, copper, chromium, arsenic, phosphorus preservative on fence posts. The addition of the zinc and phosphorus eliminated the afterglow problem caused by this treatment. However, incorporation of the phosphorus reduced the effectiveness of the decay resistance. 

Copper chromium arsenate as a wood preservative Calcium and sodium arsenate herbicides Lead arsenate formerly used on fruit crops Formerly in cotton defoliants Sodium arsenite in cattle and sheep dips Alloys with copper and lead for bearings With aluminum, gallium, and indium in semiconductors... 

Early insecticides were often inorganic arsenic, copper, lead, and sulfur compounds.6 An example is Bordeaux mixture, which contains copper sulfate and calcium hydroxide. Copper chromium arsenate is used today as a wood preservative. Organic natural products, such as pyrethrin and rotenone (11.1) have also been used. Rotenone is used today for killing undesirable fish, such as carp, before restocking ponds with game fish. Many synthetic pyrethrins are used today because of their relative safety to humans. However, both rotenone and pyrethrin7... 

It is possible that this or a similar compound could be used to replace the copper-chromium arsenate treatment now used on wood. Carvacrol is fairly volatile, bp 237°C. It would be interesting to see how fast it would be released from wood treated with it under pressure. If it is released too fast for purposes of preservation, the wood could be im-... 

A copper chromium arsenic preservative is used in industrial pretreatment of timber. This process creates the potential for operator exposure (Garrod etal. 1999) as well as the need to remediate soil contaminated with the preservative (Balasoiu etal. 2001). Potentially, further remediation is needed when the wood might be recycled for wood chips (Velizarova et al. 2002). 

CrAs04 CHROMIUM ARSENATE 557 Cs20[g] CESIUM OXIDE (GAS) 597... 

From the viewpoint of chemical and physical requirements the permissible indicators involve a number of criteria mercury, selenium, cadmium, vanadium, chromium, arsenic, silver, lead, barium, cyanides, hydrogen sulphide, fluorides, phenols, oil and oil substances, COD(Mn), colour, odour, taste and turbidity. The most stringent criterion concerns the content of mercury, followed by selenium, cadmium, vanadium, cyanides, oil and oil substances. Another important indicator is the content of organic matters characterized by COD(Mn). 

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