Arsenate cacodylic acid

Soils amended with arsenic-contaminated plant tissues were not measurably affected in C02 evolution and nitrification, suggesting that the effects of adding arsenic to soils does not influence the decomposition rate of plant tissues by soil microorganisms (Wang et al. 1984). The half-life of cacodylic acid is about 20 days in untreated soils and 31 days in arsenic-amended soils (Hood 1985). Estimates of the half-time of inorganic arsenicals in soils are much longer, ranging from 6.5 years for arsenic trioxide to 16 years for lead arsenate (NRCC 1978). 

Silvisar-510 (mixture of cacodylic acid and triethanolamine cacodylate) MALLARD, Anasplatyrhynchos Sodium arsenate... 

It has been suggested, but not yet verified, that many small mammals avoid arsenic-supplemented feeds and consume other foods if given the choice (NAS 1977), and that cacodylic acid, which has negligible effects on wildlife, reduces species diversity due to selective destruction of vegetation (Hood 1985). Both topics merit more research. 

Arsenic trioxide Arsenic trioxide Cacodylic acid Lead arsenate Total arsenic... 

Human volunteers who drank wine containing inorganic arsenic excreted methylarsonic and cacodylic acids in their urine (96). These two compounds also occur in the urine of copper smelters, the elevated arsenic content presumably coming from copper ores (97). Cacodylate ion forms when H34As04 is administered orally to dogs or hamsters (98-100). A Japanese group reported that various small animals will form methylar-sonate and cacodylate from H3ASO4 (101). On the basis of presently available data, it remains uncertain whether arsenic biomethylation occurs from the bodily processes of the mammals themselves or from microflora of the intestinal tract. 

The marine facultative anaerobe bacterium Serratia marinoruhm and the yeast Rhodotoruhi rubra both methylate arsenate ion to methylarsonate, but only the latter produces cacodylic acid (258). Human volunteers who ingested 500 fig doses of As as sodium arsenite, sodium methylarsonate, and sodium cacodylate excreted these compounds in their urine (259). Of these three, approximately 75% of the sodium arsenite is methylated, while 13% of methylarsonate is methylated. Rat liver subcellular fractions methylated sodium arsenate in vitro, providing the first direct evidence for possible mammalian methylation independent of symbiotic bacteria (260). Shariatpanahi el al. have reported kinetics studies on arsenic biotransformation by five species of bacteria (261). They found that the As(V)-As(IIl) reduction followed a pattern of two parallel first-order reactions, while the methylation reactions all followed first-order kinetics. Of the five species tested, only the Pseudomonas produced all four metabolites (arsenite, methylarsonate, cacodylate, trimethylarsine) (261). 

Arsenic trioxide finds major use in the preparation of other compounds, notably those used in agricultural applications, The compounds monosodium methylarsonate. disodium methylarsonate, methane arsenic acid (cacodylic acid) are used for weed control, while arsenic acid, H3ASO4, is used as a desiccant for the defoliation of cotton crops, Other compounds once widely used in agriculture are calcium arsenate for control of boll weevils, lead arsenate as a pesticide for fruit crops, and sodium arsenite as a herbicide and for cattle and sheep dip. In some areas, arsenilic acid has been used as a feed additive for swine and poultry. Restrictions on these compounds vary from one country and region to the next. 

Arsenic-organic Herbicides MSMA, Cacodylic Acid... 

In September 1966 The New York Times published a report that cacodylic acid, an organic arsenic containing compound, was also being used in Vietnam.49 Cacodylic acid was a defoliant that was also toxic to man. According to the Merck Index, cacodylic acid was a dimethylarsenic acid containing 54.29 per cent arsenic, and was extremely poisonous.50 Seventy grams would kill the average 150-lb man if administered subcutaneously. 

Official statements at the time, and to an extent even now, refer to only the less-toxic defoliants. However, Assistant Secretary of Defence, Cyrus Vance, when asked in 1965 whether arsenic and cyanide compounds were being sprayed over South Vietnam, replied, We are making limited use of them in the southern part of Vietnam but not yet in the north. 52 It is hard to escape the conclusion then that aerial spraying of cacodylic acid continued unabated to at least 1971 and caused unknown casualties to human and animal life below. 

For instance in the synthesis of dimethyl arsinic acid (cacodylic acid) trivalent arsenic is isomerised to the pentavalent state... 

Cacodylic acid organo arsenic Cadusafos phosphoro organic, phosphoro dithioate Camphechlor chlorinated hydrocarbon Captafol heterocyclic nitrogen, indoledione Captan heterocyclic nitrogen, indoledione Carbaryl carbamate... 

Arsenic trioxide cacodylic acid, DSMA, MSMA... 

S. Yamamoto, Y. Konishi, T. Murai, M. A. Shibata, T. Matsuda, K. Kuroda, G. Endo, S. Fukushima, Enhancing effects of an organic arsenic compound dimethy-larsenic (cacodylic acid) in a multi-organism carcinogenesis bioassay, Appl. Organomet. Chem., 8 (1994), 197-201. 

Methods of Speciation and Fractionation. It is apparent that in order to understand the mobility of arsenic and its availability for reactions, methods of speciation and fractionation must be applied to sediment samples in field and laboratory studies. In this paper speciation refers to the separation and quantitative determination of inorganic arsenic, methanearsonic acid, and cacodylic acid. Compartmentalization involves identifying the major compartments for arsenic in a heterogeneous system (e.g. aqueous, adsorbed, occluded,...) and determining the amounts of arsenic in each compartment. Fractionation involves the extraction of arsenic from operationally defined fractions of the solid phase of an aquatic system (e.g. sediment). 

Adsorption processes may be particularly important in influencing species concentrations, since the arsenic present in the pore waters will probably be in equilibrium with arsenic adsorbed on solid surfaces. Arsenic in any species measured in pore waters may be only a fraction of the total amount of that species present in the sediments, the rest being adsorbed to or incorporated into particulate matter. Thus, it is important to study the sorptive characteristics of each of the arsenic species in the sediments. In the Menominee River sediments studied, the four oxygenated arsenic species (arsenate, arsenite, monomethyl arsonic acid and cacodylic acid) are often present together and competing among themselves and with phosphate for the same sorption sites. The competitive adsorptive characteristics of the species could greatly influence... 

To illustrate this point, assume that a sediment initially contains only cacodylic acid but that there are bacteria present which convert cacodylic acid to arsenate. Assume further that cacodylic acid is not adsorbed by the sediment, while arsenate is strongly adsorbed. As the cacodylic acid is converted to arsenate, arsenate is adsorbed by the sediment and arsenic disappears from solution. Assuming a 90% water content in the sediments, an initial cacodylic acid concentration of 1000 iJi, and using the constants for arsenate given later in this paper, the amount of arsenic in solution and adsorbed on the sediments can be calculated. Results of such a calculation are listed in Table III. 

Results of Calculation of Conversion of Cacodylic Acid to Arsenate in Anaerobic Sediment... 

However, the time scales for adsorption and desorption reactions are much shorter than those for microbially mediated arsenic species transformations. Adsorption and desorption reactions reach equilibrium over a period of 24 hours or less (32, 33). On the other hand. Wool son ( ) estimated conversion rates of 0.067 to 0.404 % day"l for oxidative metabolism of cacodylic acid to arsenate in model aquatic systems. 

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