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Charles Elmer Roberson

Publications and source records attributed to Charles Elmer Roberson.

5 recordsLinked to original sources
USGS1969

Solubility of aluminum in the presence of hydroxide, fluoride, and sulfate

The total concentration of aqueous dissolved species of aluminum that will be present in equilibrium with microcrystalline gibbsite at various levels of complexing ligand concentration are shown graphically. The graphs can be used to estimate aluminum solubility, at 25?C and 1 atmosphere total pressure, when the pH of the solution, its ionic strength, and the total sulfate and fluoride concentrations are known. The standard free energy of formation of cryolite calculated from solubility experiments is --745.4 ? 1.0 kcal per mole at 25?C. Diagrams are included showing the solubility of cryolite in terms of aluminum, fluoride, and sodium concentrations. The stability fields of cryolite and microcrystalline gibbsite and their solubilities also are shown on pH-[F] diagrams.

Water Supply Paper↗
USGS1967

Form and stability of aluminum hydroxide complexes in dilute solution

Laboratory studies of solutions 4.53 x 10 -4 to 4.5 x 10 -5 molal (12.2-1.2 ppm) in aluminum, in 0.01 molal sodium perchlorate, were conducted to obtain information as to the probable behavior of aluminum in natural water. When the solutions were brought to pH 7.5-9.5 and allowed to stand for 24 hours, a precipitate was obtained which was virtually amorphous as shown by X-rays, and which had a solubility equivalent to that of boehmite. This precipitate had a hydrolysis constant (*Ks4) of 1.93 x 10 -13a. When solutions were allowed to stead at this pH range for 10 days, their precipitates gave the X-ray pattern of bayerite (*Ks4 = 1.11 > (10- 4). These hydrolysis constants were obtained at 25?C. and corrected to zero ionic strength and are in close agreement with other published values. The predominant dissolved form in this pH range is Al(OH) -4. Below neutral pH (7.0) the dissolved aluminum species consist of octahedral units in which each aluminum ion is surrounded by six water molecules or hydroxide ions. Single units such as Al(OH2)6 + 3 and AlOH(OH2)5+2 are most abundant below pH 5.0, and where the molar ratio (r) of combined hydroxide to total dissolved aluminum is low. When r is greater than 1.0, polymerization of the octahedral units occurs. When r is between 2.0 and 3.0, solutions aged for 10 days or more contained colloidal particles between 0.10 and 0.45 ? in diameter. Particles whose diameters were greater than 0.10 ? were identified by X-ray diffraction as gibbsite. Particles smaller than 0.10 ? were also present and were shown by means of the electron microscope to have a hexagonal crystal pattern. Structured material consisting of sheets of coalesced six-membered rings of aluminum ions held together by double OH bridges has a distinctive kinetic behavior. This property was used to determine amounts of polymerized material in solutions having r between 1.0 and 3.0 after aging times ranging from a few hours to more than 4 months. Aging increased the size and orderliness of the polymeric aggregates and was accompanied by a decrease in the pH of the solution. The kinetic experiments and stoichiometric data for solutions aged for long periods provided a means of determining activities of polymerized aluminum. From these values the solubility product for microcrystalline gibbsite was determined to be 2.24 x 10 -3, and its free energy of formation, -? 272.3 0.4 kcal per mole. Where polymerization was observed, the process did not stop with small polynuclear complexes containing a few aluminum ions, but proceeded with aging until macromolecules or colloidal-sized particles were formed.

Water Supply Paper↗
USGS1964

Chemical composition of snow in the northern Sierra Nevada and other areas

Melting snow provides a large part of the water used throughout the western conterminous United States for agriculture, industry, and domestic supply. It is an active agent in chemical weathering, supplies moisture for forest growth, and sustains fish and wildlife. Despite its importance, virtually nothing has been known of the chemical character of snow in the western mountains until the present study. Analysis of more than 100 samples, most from the northern Sierra Nevada, but some from Utah, Denver, Colo., and scattered points, shows that melted snow is a dilute solution containing measurable amounts of some or all of the inorganic constituents commonly found in natural water. There are significant regional differences in chemical composition; the progressive increase in calcium content with increasing distance eastward from the west slope of the Sierra Nevada is the most pronounced. The chemical character of individual snowfalls is variable. Some show predominant influence of oceanic salt; others show strong effects of mineralization from continental sources, probably largely dust. Silica and boron were found in about half the samples analyzed for these constituents; precipitation is seldom analyzed for these substances. Results of the chemical analyses for major constituents in snow samples are summarized in the following table. The median and mean values for individual constituents are derived from 41-78 samples of Sierra Nevada snow, 6-18 samples of Utah snow, and 6-17 samples of Denver, Colo., snow. The sodium, chloride, and perhaps boron found in snow are probably incorporated in moisture-laden air masses as they move over the Pacific Ocean. Silica, although abundant in the silicate-mineral nuclei found in some snowflakes, may be derived in soluble form largely from dust. Calcium, magnesium, and some bicarbonate are probably added by dust of continental origin. The sources of the other constituents remain unknown. When snowmelt comes in contact with the lithosphere, the earlier diversity of chemical type largely disappears. The melt water rapidly increases its content of dissolved solids and becomes calcium magnesium bicarbonate in type. Silica, whose concentration increases more than tenfold, shows the largest gain; calcium and bicarbonate contents also increase markedly. Most of the additional mineral matter is from soft and weathered rock; bicarbonate, however, is largely from the soil atmosphere. Investigators, some reporting as much as a century ago, concentrated attention largely on nitrogen compounds and seldom reported other constituents except chloride and sulfate. The Northern European precipitation-sampling network provides the most comprehensive collection of data on precipitation chemistry, but it does not segregate snow from other forms of precipitation. The present study establishes with confidence the chemical character of snow in the Sierra Nevada, and suggests that the dissolved-solids content of precipitation increases with increasing distance inland from the Pacific Coast.

Arizona, California, Colorado, Nevada, Oregon, Uta↗