A.D. Shendrikar

Adsorption characteristics of traces of barium, beryllium, cadmium, manganese, lead and zinc on selected surfaces

Abstract The adsorption characteristics of Ba, Be, Cd, Mn, Pb and Zn on Pyrex, flint glass and polythene surfaces during storage under different conditions are described. It is concluded that the method of stabilization of water samples recommended by EPA, i.e. addition of 5 ml of 16 M HNO 3 per liter, is satisfactory. Stabilization and concentration with a mixed ligand system is recommended, except for Mn and Ba which are not extracted quantitatively. Extraction with APDC and MIBK is unsatisfactory for storage purposes.

A study of adsorption characteristics of traces of chromium(III) and (VI) on selected surfaces

Abstract The adsorption losses of chromium(III) or (VI) on the walls of Pyrex, flint glass and polyethylene beakers have been investigated. Chromium(III) or (VI) solutions were stored in beakers at different hydrogen ion concentrations, and losses due to adsorption were measured at various contact times by counting the γ-ray activity from chromium-51 radiotracer. At pH 6.95, chromium(III) solutions showed the greatest instability, particularly in polyethylene beakers, where losses up to 25% were observed at the end of the 15-day contact period. Chromium(VI) showed a completely different pattern; losses less than 1% were observed at the end of 15 days on all the three types of containers.

The determination of sulfuric acid aerosols

Abstract A reliable method has been developed for the chemical determination of sulfuric acid aerosol by simple technique and inexpensive equipment. A similar method is also presented for determining total acidity, including sulfuric acid and volatile acids together with salts that hydrolyze to give protons. The determinations can be performed directly on air samples collected with a sequential tape sampler. The basic chemical reactions involved are specifically controlled by the protons: stoichiometric amounts of bromine are released from a mixture of bromate-bromide by the protons, and the liberated bromine reacts with fluorescein to produce eosin, the color intensity of which is a direct measure of proton concentration. The detection limit for both the methods is 0.5 μg in terms of sulfuric acid and the range for quantitative measurement is 1–10 μg. The new methods are of special significance because of previous lack of reliable methods for determining acidic species in a polluted atmosphere.

Microdetermination of lead with dithizone and the ring-oven technique

Abstract A method for the microdetermination of lead with dithizone by the ring-oven technique is presented. The limit or detection is 0.04 μg and the range is 0.05–1.0 μg, of lead with no interference from other species that are of significance in air pollution studies. The determinations can be made directly on samples collected on sequential tapes. The applicability and reliability of this method for air pollution studies were verified by analyzing Mexican air samples simultaneously by atomic absorption spectrometry and the ring oven. The data show good agreement. This method is especially recommended for field studies because it is sensitive, rapid, reliable and far less expensive than methods currently in use for lead determinations.

Determination of Selenium in the Smoke from Trash Burning

Abstract The smoke resulting from open trash burning operations was analyzed for its selenium content. Selenium (as its oxides) was efficiently trapped by impingement into distilled water and determined by a methylene blue catalytic method. The data obtained show a relationship between the selenium content of the smoke and the burning material. Concentrations as high as 273 μg/m3 of selenium dioxide were found when dry wood chips were burned. The reaction of selenium oxides in humid atmospheres and in the moist tissues of the respiratory tract forms selenic or selenious acids and must be regarded as a definite health hazard.

Radiochemical evaluation of the separation of H2SO4 aerosol by microdiffusion from various filter media

SummaryA series of filter media were tested for their utility as surfaces to diffuse H2SO4. Those filter media studied were: soft glass plate, Gelman A glass fiber filter paper, 5.0μ Mitex (teflon), 0.5μ Solvinert, 1.0μ Nucleopore, Whatman 41 and Poco graphite filter. Time from 1 to 6 hours and temperature from 100° to 195° were investigated. It was found that the Mitex and the Poco graphite had the best diffusion characteristics, but both exhibit the same lower limit.ZusammenfassungFiltermaterial verschiedener Art wurde hinsichtlich seiner Brauchbarkeit als Oberfläche zur Diffusion von Schwefelsäure geprüft, u. zw.: Weichglasplatten, Glasfaserpapier A nach Gelman, 5,0-μ-Mitex (Teflon), 5-μ-Solvinert, 1,0-μ-Nucleopor, Whatman 41 und Poco Graphitfilter. Die Versuchsdauer betrug 1—6 Stunden, die Temperatur 100–195°. Mitex und Graphit zeigten die beste Diffusionscharakteristik, aber beide zeigen die gleiche Diffusionsuntergrenze.

Selenium in Papers, Cigarette Papers and Tobaccos

Abstract The selenium content of various types of papers including cigarette papers has been determined. The selenium content of representative tobaccos from different parts of the world has also been determined. Samples were processed by decomposing them by means of the oxygen flask combustion technique. After excess oxygen was eliminated the selenium content was determined by means of the catalytic method of West and Ramakrishna (16). The selenium content of cigarette papers was found to range from 0.87 to 2.11 ppm (as SeO2) while filter papers and newspapers were found to contain from 0.21 to 1.38 ppm. The selenium content of most tobaccos fell somewhere in the range of 0.46 to 1.20 ppm. The Indian crude cigarette (Beedi) was found to contain as high as 4.10 ppm. Discussion of the findings includes some observations on possible health significance of selenium in smoke. Comments are included regarding the hazards of cigarette smoking as compared to those of cigar and pipe smoking.

Separation and purification of beryllium by the fractional sublimation of beryllium acetylacetonate

Abstract Solutions containing beryllium(II) in admixture with most common metals can be treated with acetylacetone to form the beryllium and various other acetyl-acetonates which precipitate. The precipitate is filtered, washed, dried and fractionally sublimed in a special sublimator. After sublimation with air as a carrier gas the beryllium acetylacetonate fraction is recoverable in high purity. Zinc is the only detectable contaminant by atomic absorption spectrometry but can be eliminated by masking with ammonium thiocyanate before the formation of the metal acetylacetonates. Beryllium fractions were checked for purity by atomic absorption spectrometry and found to contain less than 0.002% Zn after a single sublimation. The method appears to offer an excellent method of purification for beryllium if quantitative recoveries are not required.

Extraction studies of platinum group metals with diantipyrylpropylmethane

Abstract Diantipyrylpropylmethane (DAPM) is easily synthesized and forms reasonably stable solutions in a number of common organic solvents. The solubility of DAPM in ten different solvents is reported. Solutions of DAPM react with the anionic chloro complexes of the platinum group metals in hydrochloric acid solution to form stable extractable complexes. The distribution of tracer quantities of the six platinum metals between hydrochloric acid solutions and a chloroform solution of the DAPM was studied. Distribution coefficients are reported as a function of the hydrochloric acid concentration; 98% of the Os, Pt or Pd can be extracted in a single pass, over an acid concentration range 0.1–12 M ; 98% Ir can be extracted in one extraction over the acid range 0.1–6 M . Ruthenium can be extracted quantitatively in one extraction from 4–6 M hydrochloric acid with a stronger DAPM solution. Rhodium is poorly extracted under all conditions tested. DAPM is not promising for the selective separation of mixtures of platinum group metals, but may be used for group extraction.