Water arsenical

Dissolved arsenic is correlated with ammonia (Fig. 4), consistent with a release mechanism associated with the oxidation of organic carbon. Other chemical data not shown here provide clear evidence of iron, manganese and sulfate reduction and abundant methane in some samples indicates that methanogenesis is also occurring. It is not clear however if arsenic is released primarily by a desorption process associated with reduction of sorbed arsenic or by release after the reductive dissolution of the iron oxide sorbent. Phreeqc analysis shows PC02 between 10"12 and 10"° bars and that high arsenic waters are supersaturated with both siderite and vivianite. 

Potential for contamination of deep aquifers in Bangladesh by pumping-induced migration of higher arsenic waters... 

Ramaswami, A., Tawachsupa, S. and Isleyen, M. (2001) Batch-mixed iron treatment of high arsenic waters. Water Research, 35(18), 4474-79. 

WATER — Arsenical Water. The Green Lion of the Philosophers. 

Yamamura S. (2003) Drinking water guidelines and standards. In Arsenic, Water, and Health the state of the art (eds. H. Hashizume and S. Yamamura). World Health Organisation, chap. 5. 

In natural waters arsenic usually occurs at concentrations ranging from units to tens of /xg Mineral waters containing more than 0.7 mg l of arsenic are called arsenic waters. Since the compounds of arsenic appear in company with phosphates, used as additives in detergents, as much as... 

Song, S., Lopez-Valdivieso, A., Hemandez-Campos, D.X, Peng, C., Monroy-Fernandez, M.G. Razo-Soto, 1. (2006) Arsenic removal from high-arsenic water by enhanced coagulation with ferric ions and coarse calcite. Water Research, 40 (2), 364-372. 

Analytical work is much aggravated by the different states of preservation of the chemical agents inside and outside of the container walls and by the fact that the assortment includes chemical munitions captured from the Allies as well as German munitions. Nevertheless, because of other priorities, little basic research has been done. Analytical work has been mainly confined to determination of total arsenic, water soluble arsenic, and residual mustard (i.e., that does not pour out). 

Arsenic(III) oxide is slightly soluble in water, giving a solution with a sweetish taste—but as little as 0.1 g can be a fatal dose (The antidote is freshly-precipitated iron(III) hydroxide.) The solution has an acid reaction to litmus, due to the formation of arsenic(III) acid ... 

On concentrating the solution, a solid of formula As40jq. SH O (which may be composed by hydrated arsenic(V) acid) is obtained, and this, on fairly prolonged heating to 800 K, loses water and leaves arsenic(V) oxide. No compounds corresponding to the other acids of phosphorus are formed, but salts are known. 

It dissolves in water to give arsenic(V) acid, and in alkalis to form arsenates V). 

Arsenic(III) (arsenious) acid, H3ASO3.—When arsenic(III) oxide is dissolved in water the corresponding acid is formed ... 

Arsenic(V) acid, H3ASO4 (strictly, tetraoxoarsenic(V) acid) is obtained when arsenic is oxidised with concentrated nitric acid or when arsenic(V) oxide is dissolved in water. It is a moderately strong acid which, like phosphoric V) acid, is tribasic arsenates V) in general resemble phosphates(V) and are often isomorphous with them. 

Arsenic trichloride is not completely hydrolysed by water, and in solution the following equilibrium is set up ... 

When sulphur is melted viscosity changes occur as the temperature is raised. These changes are due to the formation of long-chain polymers (in very pure sulphur, chains containing about 100 (X)0 atoms may be formed). The polymeric nature of molten sulphur can be recognised if molten sulphur is poured in a thin stream into cold water, when a plastic rubbery mass known as plastic sulphur is obtained. This is only slightly soluble in carbon disulphide, but on standing it loses its plasticity and reverts to the soluble rhombic form. If certain substances, for example iodine or oxides of arsenic, are incorporated into the plastic sulphur, the rubbery character can be preserved. 

Both chloramine-T and dichloramine-T have marked antiseptic properties, chloramine-T being most frequently used because of its solubility in water. Aqueous solutions of chloramine-T can be used either for external application, or for internal application to the mouth, throat, etc, as chloramine-T in moderate quantities is non-toxic its aqueous solution can also be effectively used when the skin has come in contact with many of the vesicant liquid poison-gases, as the latter are frequently organic sulphur or arsenic derivatives which combine with or are oxidised by chloramine-T and are thus rendered harmless. 

Optional experiment. When all the air has been displaced, collect a test-tube of the gas over water (by appropriate inclination of the end of the delivery tube beneath the mouth of a test-tube filled with water and supported in a beaker of water). Observe the colour and odour of the gas. Ignite the test-tube of gas, and note the luminosity of the flame and the amount of carbon deposited. Pure acetylene is almost odourless the characteristic odour observed is due to traces of hydrides of phosphorus, arsenic and sulphur. 

The arsenic acid solution is prepared by dissolving 123 g. of arsenic pentoxide in 104 ml. of water 100 ml. of the cold solution are used in the experiment. 

It is usually preferable to oxidise the compound directly as follows. Intimately mix 0 02-0 05 g. of the eompound with 3 g. of sodium peroxide and 2 g. of anhydrous sodium carbonate in a niekel erucible. Heat the crueible and its eontents with a small flame, gently at first, afterwards more strongly until the eontents are fused, and eontinue heating for a further 10 minutes. Allow to stand, extract the contents of the crucible with water, and filter. Add exeess of eoneentrated nitrie acid to the filtrate and test with ammonium molybdate reagent as above. A yellow preeipitate indicates the presenee of phosphorus. It must be borne in mind that the above treatment 1 eonvert any arsenie present into arsenate. 

It is recommended that the eompound be fused with a mixture of sodium carbonate (2 parts) and sodium peroxide (1 part) as in the test for Plvoaphoms. Extract the fused mass with water, filter, and acidify with dilute hydrochloric acid. Pass hydrogen sulphide through the hot solution arsenic is precipitated as yellow arsenic sulphide. If antimony is present, it will be precipitated as orange antimony trisulphide. 

A major advantage of this hydride approach lies in the separation of the remaining elements of the analyte solution from the element to be determined. Because the volatile hydrides are swept out of the analyte solution, the latter can be simply diverted to waste and not sent through the plasma flame Itself. Consequently potential interference from. sample-preparation constituents and by-products is reduced to very low levels. For example, a major interference for arsenic analysis arises from ions ArCE having m/z 75,77, which have the same integral m/z value as that of As+ ions themselves. Thus, any chlorides in the analyte solution (for example, from sea water) could produce serious interference in the accurate analysis of arsenic. The option of diverting the used analyte solution away from the plasma flame facilitates accurate, sensitive analysis of isotope concentrations. Inlet systems for generation of volatile hydrides can operate continuously or batchwise. 

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