Skip to main content

Currently Skimming:

Appendix C: Determining Traces of Arsenic in Natural Materials
Pages 255-262

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 255...
... Because a single mean value is desired for the concentration of each arsenical species of interest, the sample must be homogenized and a subsample of suitable size for analysis must be taken. To minimize contamination, unused sample material should be stored in 255
From page 256...
... Natural water often contains suspended matter, which must be either filtered out or allowed to remain. If the particles filtered from an air stream contain volatile forms of arsenic, consideration must be given to the losses that may occur at the temperatures and air velocities to which the particles are exposed on the filter and to the duration of exposure (arsenic trioxide has a vapor pressure of 0.68 mm Hg at 200 C)
From page 257...
... Quartz can be attacked without metallic contamination by vaporphase treatment with hydrofluoric acid and nitric acid in a closed system.89~ This approach was therefore tried with slag, albeit with some misgivings regarding the volatility of arsenic fluorides. No losses or contamination seem to have occurred, however, inasmuch as the results obtained on fly ash agreed well with those obtained with neutron activation and sulfuric acid leaching.245 Procedures for digesting plant or animal tissues for determining total arsenic must completely convert the arsenic to inorganic form (preferably arsenate)
From page 258...
... Coprecipitation with ferric hydroxide, Fe(OH) 3, has long been known to collect pentavalent arsenic quantitatively from solution at concentrations as low as 2 ng/ml.643 652 The hydroxides of cerium and zirconium appear to be as effective as ferric hydroxide in this regard.649 Thionalide can collect arsenic efficiently from comparatively large amounts of seawater, 652 but this reagent apparently does not function well at low salt concentrations.779 Trivalent arsenic can readily be extracted from 6 N hydrochloric acid with mixtures of ketone and carbon tetrachloride.276 At lower acidities (pH, 2-6)
From page 259...
... Moreover, this blank response diminishes with the age of the solution. The fading of the blank response due to arsenic in the sodium borohydride appears to result from the gradual adsorption of dissolved arsenic onto suspended impurities in the reagent solution.
From page 260...
... Feldman, personal communication) , giving absolute and concentrational detection limits of 0.5 ng and 25 pa/ml, respectively.
From page 261...
... , chemical-group separations can still be performed to isolate the arsenic-76 activity.350 604 Electrochemical Methods In the electrochemical methods that have been proposed for determining traces of arsenic, the arsenic is usually first isolated by volatilization or extraction, then converted to the trivalent form and determined polarographically.27 The most sensitive such technique is differential pulse polarography, which has a detection limit of about 0.3 ng of arsenic per milliliter and can be used in the presence of natural pollutants, such as unfiltered sludge.57~608 Gas Chromatography Total arsenic can be determined by gas chromatography if the arsenic is first collected and converted to triphenylarsine. The collectionconversion procedure is somewhat long, but the absolute limit of detection is quite low (20 pa)


This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More information on Chapter Skim is available.