Arsenic acid Aqueous solution

The oxidation of arsenopyrite [FeAsS] releases both sulfur and arsenic. Buckley and Walker (1988) studied the oxidation of arsenopyrite in alkaline and in acidic aqueous solutions. In air, the mineral reacted rapidly, and the oxidation of arsenic to As(III) was more rapid than the oxidation of iron on the same surface. Only a small amount of sulfur oxidation occurred. Under acidic conditions, the mineral formed sulfur-rich surfaces. 

ARSENATE of LEAD (7784-40-9) Decomposes on contact with acids or acid fumes, emitting arsenic fumes. Contact with strong oxidizers may cause fire and explosions. Violent reaction with sodium acetylide. Incompatible with mercurous chloride. May form impact-sensitive explosive materials with ethanediamine, A.A -dinitro-, pyrogallic acid. Aqueous solutions decompose on contact with active metals, emitting fumes of arsenic. 

In aqueous solution arsenic(lll) oxide is a reducing agent being oxidised to arsenate(V) by halogens, chlorate(I), nitric acid and even iron(III) chloride. 

In metallic form, barium is very reactive, reacting readily with water to release hydrogen. In aqueous solution it is present as an ion with a +2 charge. Barium acetate, chloride, hydroxide, and nitrate are water-soluble, whereas barium arsenate, chromate, duoride, oxalate, and sulfate are not. Most water-insoluble barium salts dissolve in dilute acids barium sulfate, however, requkes strong sulfuric acid. 

A flow-injection system with electrochemical hydride generation and atomic absorption detection for the determination of arsenic is described. This technique has been developed in order to avoid the use sodium tetrahydroborate, which is capable of introducing contamination. The sodium tetrahydroborate (NaBH ) - acid reduction technique has been widely used for hydride generation (HG) in atomic spectrometric analyses. However, this technique has certain disadvantages. The NaBH is capable of introducing contamination, is expensive and the aqueous solution is unstable and has to be prepared freshly each working day. In addition, the process is sensitive to interferences from coexisting ions. 

Compounds of Tl have many similarities to those of the alkali metals TIOH is very soluble and is a strong base TI2CO3 is also soluble and resembles the corresponding Na and K compounds Tl forms colourless, well-crystallized salts of many oxoacids, and these tend to be anhydrous like those of the similarly sized Rb and Cs Tl salts of weak acids have a basic reaction in aqueous solution as a result of hydrolysis Tl forms polysulfldes (e.g. TI2S3) and polyiodides, etc. In other respects Tl resembles the more highly polarizing ion Ag+, e.g. in the colour and insolubility of its chromate, sulfide, arsenate and halides (except F), though it does not form ammine complexes in aqueous solution and its azide is not explosive. 

As an alternative, a reversible indicator may be employed, either (a) 1-naphthoflavone (0.5% solution in ethanol, which gives an orange-coloured solution at the end-point), or (b) p-ethoxychrysoidine (0.1% aqueous solution, colour change pink to pale yellow). Under these conditions, the measured 25 mL portion of the arsenic solution is treated with 10 mL of 10 per cent potassium bromide solution, 6 mL of concentrated hydrochloric acid, 10 mL of water and either 0.5 mL of indicator (a) or two drops of indicator (b). 

Reactions in aqueous solution can have complicated kinetics. An example Is the reaction between arsenic acid and iodide ions ... 

The neutron activation method for the determination of arsenic and antimony in seawater has been described by Ryabin et al. [66]. After coprecipitation of arsenic acid and antimony in a 100 ml sample of water by adding a solution of ferric iron (10 mg iron per litre) followed by aqueous ammonia to give a pH of 8.4, the precipitate is filtered off and, together with the filter paper, is wrapped in a polyethylene and aluminium foil. It is then irradiated in a silica ampoule in a neutron flux of 1.8 x 1013 neutrons cm-2 s 1 for 1 - 2 h. Two days after irradiation, the y-ray activity at 0.56 MeV is measured with use of a Nal (Tl) spectrometer coupled with a multichannel pulse-height analyser, and compared with that of standards. 

To obtain MSMA, the DSMA solution is partially acidified with sulfuric acid and the resulting solution concentrated by evaporation. As the aqueous solution is being concentrated, a mixture of sodium sulfate and sodium chloride precipitates out (about 0.5 kg per 100 kg of active ingredient). These salts are a troublesome disposal problem because they are contaminated with arsenic. The salts are removed by centrifugation, washed in a multistage, countercurrent washing cycle, and then disposed of in an approved landfill. 

Commercial arsenic acid is usually the orthoarsenic acid [7774-M1-6] corresponding to the above hemihydrate formula. The aqueous solution of this acid behaves as a triprotic acid the dissociation constants, Ki, K2 and K3 being 5.6x10-3, 1.7x10 and 3.OxlO-i, respectively. The meta and pyro forms... 

The aqueous solution of arsenic pentoxide is arsenic acid which probably corresponds to the hemihydrate formula H3ASO4 O.5H2O. See Orthoarsenic acid. It behaves as a triprotic acid forming various arsenate derivatives of metals. 

The aqueous solution is highly acidic, pH of 0. IN solution is 1.1. It readily decomposes to arsenic trioxide, elemental arsenic and iodine when heated in air at 200°C. The decomposition, however, commences at 100°C ... 

Hydrogen sulfide forms precipitates of several metal sulfides when passed through an aqueous solution of metal salts. Under acid conditions, several metals including arsenic, antimony, bismuth, cadmium, copper, lead, mercury, and tin are precipitated as their sulfide e.g. ... 

All the condensed arsenates resulting in this way are hydrolyzed to orthoarsenate not only in aqueous solution but also on exposure to moist air. The acid triarsenate is an intermediate but not the pyroarsenate (310). Clearly the triarsenate is marked by special stability, for triarsenic acid, H5AS3O10, also occupies a special place in the series of hydration products form arsenic(V) oxide (269, 310). 

The compounds MMA, DMA, and TMAO are reduced in acidic aqueous media by borohydride solutions to methylarsine (MeAsH2, bp 2°C), dimethylarsine (Me2AsH, bp 35°C), and trimethylarsine (Me3As, bp 55°C), respectively. These products are useful derivatives for speciation analysis of arsenic because they are readily separated from complex sample matrices and may be further separated from each other by distillation (41) or by gas chromatography (42) prior to their determination by element-specific detectors. Consequently, arsine generation techniques are the most commonly used methods for determining MMA, DMA, and TMAO in marine samples. 

As regards the nature of their action on a human organism, tellurium and its compounds are similar to the inorganic compounds of selenium and arsenic. Hydrogen telluride is the most toxic. Tel-lurium(IV) oxide and aqueous solutions of the salts of tellurous and telluric acids are also toxic. Only tellurium ( metallic ) is not toxic if it gets into an organism. 

What ions are present in an aqueous solution of arsenous acid anhydride Write the equations of the reactions. 

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