Arsenic content

Elemental phosphoms from the electrothermal process is a distilled product of high purity and yields phosphoric acid pure enough for most industrial uses without any further treatment. The main impurity is ca 20—100 ppm arsenic present in the phosphoms as the element and in the phosphoric acid as arsenious acid. To remove the arsenic, the phosphoric acid destined for food, pharmaceutical, and some industrial-grade appHcations is treated with excess hydrogen sulfide, filtered, and blown with air to strip out excess H2S. This treatment generally reduces the arsenic content of the phosphoric acid to less than 0.5 ppm. The small amount of filter cake is disposed of in approved chemical landfills. 

Raki, a Turkish alcoholic drink was also analyzed by differential pulse polarography and copper, iron and zinc could be determined. For the arsenic content in beer a more sensitive method had to be applied. For this method a new catalytic method is established and the arsenic content was determined by using this new method. 

Phosphoric acid esters having a low content of arsenic can be obtained by treating with 0.1-10% adsorbents such as activated clay, active carbon, alumina, and silica gel to decrease the arsenic content. Thus, 100 parts lauryl phosphate containing 10.3 ppm As and 2 parts activated clay were mixed at 60-70°C for 2 h and filtered to give lauryl phosphate only containing 0.6 ppm As [28]. 

Activity Tests. Figure 2 shows results of activity tests for a commercial American Cyanamid HDS-2 catalyst which had been in use for about six years. The catalyst was sampled at various depths and results for three samples containing 0.01% As, 0.6% As, and 3.6% As show a decrease in activity with Increasing arsenic content. 

Table 9.5. Arsenic contents of the lithosphere and world soils (Data from Han et al., 2003b, with kind permission of Springer Science and Business Media)...

Single more reflective Fe-oxhyhdroxide identified appears to be mixture of nanocrystalline hematite and ferrihydrite with relatively low arsenic content (6.7%As205). 

Lewisite is generally considered a suspect carcinogen because of its arsenic content. 

The arsenic content of benzoic acid is determined using USP general test <211>, Method II, and approved substances cannot contain more than 3 ppm. 

Selenium is one of the better decolorizers in tank melting. The iron is neutralized by the pink tint of the selenium. Since a yellow shade is still present, the decolorizing is completed with the addition of a small amount of cobalt. Arsenic helps to stabilize the decolorizing with selenium but as the arsenic content increases more selenium is required. 

At the next dinner party, as your host proudly serves the lobster thermidor, you may wish to momentarily stray from the conventions of a polite but conservative guest, the archetypal chemist, by casually inquiring about the arsenic content of the meal. Given arsenic s reputation as a potent poison, your host may be affronted or bemused, but he or she is sure to be interested. 

Although there had been earlier reports (1-3) of the presence of arsenic in marine samples, the first comprehensive study was presented by Jones (4) in 1922. He examined marine algae collected from British coastal waters, reporting concentrations of arsenic and information on its extraction with water and ethanol. He referred to the arsenic as organic arsenic and, perhaps somewhat mischievously, remarked that the reputed medicinal properties of some algae may be due to their organic arsenic content. 

Clearly the procedures of the laboratories involved in this project could be improved. Before suggesting methods of improvement, one obvious point should be stressed. The results of this study do not vitiate the use of data between laboratories they merely indicate that the data should be used with caution. For example, in the Luristan bronzes (14), the arsenic content of arsenical copper artifacts is said to drop from 2-6% to 2% and below after a tin-copper alloy was introduced about 2600 B.C. If another laboratory analyzes a copper alloy object and finds, say 4.9% arsenic (and all other factors agree), the object can be confidently set into the earlier group if the laboratory finds 0.8% arsenic, the object could be set into the later group. If the arsenic content is 1.95%, the grouping into which it would fall is less unequivocal, and other factors... 

Name. Approximate Composition. Hardness (Mohs Scale). Density. Usual Form. Arsenic Content, per cent. Approx. 

The absorption of arsenic by marine algae has been referred to (p. 18) certain Chinese medicinal algae have an exceptionally high arsenic content.9... 

Expressed as arsenic content of ore. f Wiute arsenic and arsenic soot. 

Zinc Arsenites.—When a mixture of zinc oxide and arsenious oxide is heated, combination occurs 4 at about 250° C. the metarsenite is formed, and at about 42Cr C. the orthoarsenite is the product. At higher temperatures oxidation occurs 5 and at. 500° C. As and AsT are present in approximately equal amounts, although the total arsenic content is reduced owing to volatilisation. At 600° C. the product contains only Asr, and with rising temperature the rate of combination rises to a maximum at 700° C., thereafter remaining constant. 

Absorption of arsenic by the bones also occurs to a considerable extent,6 and their arsenic content, whether death occurs after a few hours or only after some days, may give valuable information where suspicion of poisoning exists. Thus in the case of a man who died 8 days after ingesting the poison, 110 mg. of arsenic were found in the bones, about half being present in the bones of the arms and legs and about 20 per cent, in the flat bones of the skull but in the case of a woman who died after 12 horns, out of a total of 1907 mg. found in the body only 3-2 mg. occurred in the bones,7 but this amount was more than was found in any other portion of the body (except the skin) not in direct contact with the alimentary canal. In experiments on dogs to which arsenic had been administered, Popp showed 8 that the amount of arsenic in the calcined bones was about one-sixth of the amount found in the bones before cremation, and less than one-thousandth of the total amount in the whole body before cremation. 

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