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Mary H. Fletcher

Publications and source records attributed to Mary H. Fletcher.

At least 19 recordsLinked to original sources
USGS2002

Characteristic constants of 2,2',4'-trihydroxyazobenzene-5-sulfonic acid, a reagent for spectrophotometric analysis

The dye 2,2',4'-trihydroxyazobenzene-5-sulfonic acid, has shown promise as a reagent for the determination of zirconium. As the literature contains very little information about this dye, basic data pertinent to its use as a reagent were determined. The sulfonic acid group and all three of the hydroxy groups show acidic characteristics. Apparent dissociation constants were determined for the three more labile protons and the approximate order of magnitude for the fourth constant was estimated. Absorption spectra for the different ionization species are given. A curve is also included which shows the fraction of dye in the different ionization forms at acidities from 10.35M hydrochloric acid to pH 11.9. A sixth dye species was found in 1.0 to 8.4M potassium hydroxide solutions, but its nature is unknown.

Analytical Chemistry↗
USGS2002

Theoretical stusy of the reaction between 2,2',4' - trihydroxyazobenzene-5-sulfonic acid and zirconium

Zirconium reacts with 2,2',4'-trihydroxyazobenzene-5-sulfonic acid in acid solutions to Form two complexes in which the ratios of dye to zirconium are 1 to 1 and 2 to 1. Both complexes are true chelates, with zirconium acting as a bridge between the two orthohydroxy dye groups. Apparent equilibrium constants for the reactions to form each of the complexes are determined. The reactions are used as a basis for the determination of the active component in the dye and a graphical method for the determination of reagent purity is described. Four absorption spectra covering the wave length region from 350 to 750 mu are given, which completely define the color system associated with the reactions in solutions where the hydrochloric acid concentration ranges from 0.0064N to about 7N.

Analytical Chemistry↗
USGS2002

Thoron-tartaric acid systems for spectrophotometric determination of thorium

Thoron is commonly used for the spectrophotometric determination of thorium. An undesirable feature of its use is its high sensitivity to zirconium. This study describes the use of tartaric acid as a masking reagent for zirconium. Three tartaric acid-thoron systems, developed for the determination of thorium, differ with respect to the concentrations of thoron and tartaric acid. Mesotartaric acid, used in one of the systems, is most effective in masking zirconium. The behavior of rarer elements, usually associated with thorium ores, is determined in two systems, and a dilution method is described for the direct determination of thorium in monazite concentrates.

Analytical Chemistry↗
USGS2002

Thoron-meso-tartaric acid system for determination of thorium

In the spectrophotometric determination of thorium with thoron, meso -tartaric acid is used as a masking reagent for zirconium. The effects of different experimental variables such as the concentrations of the reagents, time, and temperature, and the behavior of 35 ions which might be present in thorium ores are discussed. A dilution procedure is given for the direct determination of thorium in zircon (ZrSiO 4 ) that is also generally applicable to other materials.

Analytical Chemistry↗
USGS1956

A fluorimetric study of the thorium-morin system

Thorium reacts with morin to yield a yellow complex that fluoresces when irradiated with ultraviolet light. The effect on the fluorescence of such variable as concentration of acid, alcohol, thorium, morin, and complex; time, temperature, and wavelength of exciting light are studied to determine experimental conditions yielding maximum fluorescence. The effects of Zr 4+ , Al 3+ , Fe 3+ , Ca 2+ , and La 3+ are discussed. The fundamental relationships between light absorption and fluorescence are expressed in a general equation which applied to a three-component system when the fluorescence is measured in a transmission-type fluorimeter. This general equation is used to obtain an expression for the fluorescence of the thorium-morin system. Equations, derived from experimental data, related both the fraction of thorium reacted to form complex and the fraction of unquenched fluorescence to the concentration of uncombined morin. These functions, when combined with the general equation, give an expression which relates the total net fluorescence to the amount of uncombined morin in the solution. This last equation can be used to determine the one region for the concentration of uncombined morin that gives maximum sensitivity for the system. Calculated standard curves are in excellent agreement with experimental curves.

Trace Elements Investigations↗
USGS1955

The thoron-tartaric acid systems for the spectrophotometric determination of thorium

Thoron is popularly used for the spectrophotometric determination of thorium. An undesirable feature of its use is the high sensitivity of the reagent toward zirconium. This study describes the use of tartaric acid as a masking reagent for zirconium. Three tartaric acid-thoron systems, developed for the determination of thorium, differ with respect to the concentrations of thoron and tartaric acid. Mesotataric acid, used in one of the systems, is found to be most effective in masking zirconium. The behavior of various rarer elements, usually found associated with thorium ores, is determined in two of the systems, and a dilution method is described for the direct determination of thorium in monazite concentrates.

Trace Elements Investigations↗
USGS1954

A spectrophotometric study of the thorium-morin mixed-color system

Thorium reacts with morin in solutions at a pH of 2.0 to yield a single complex that has a thorium:morin ratio of 1:2. The yellow complex has a maximum absorbance at 410 m and is stable for at least 7 hours. The sensitivity of the reaction is such that as little as about 0.2 microgram of ThO 2 in 50 ml can be determined using a light path of 5 cm. An average apparent equilibrium constant of approximately l x 10 6 was found for the reaction. The effects of acidity, alcohol content, morin content, time, age of the morin reagent and temperature of the reaction have been studied as have the effect of some other ions. Zirconium and aluminum interfere seriously and must be absent. The interference from ferric iron is also serious but the effect may be appreciably decreased if hydroxylamine is added to the solution. Relatively large amounts of calcium and lanthanum may be present without causing interference, and these ions can be used as carriers in separations of thorium from other ions. Morin is a suitable reagent for the determination of thorium in pure solutions. If appropriate separations are found for the separation of thorium from other ions, the reaction will be useful for the determination of trace amounts of thorium in complex materials. The information presented in this paper is fundamental to any specific adaptation of the reaction to the analysis of complex materials.

Trace Elements Investigations↗
USGS1953

A fluorimeter for solutions

description of and complete drawings for the construction of a fluorimeter for the measurement of fluorescence of solutions are given. The instrument is sturdy and versatile. It may be used with various phototubes and measuring devices. It is constructed so that phototubes and filters may be changed readily. Sensitivity is controlled easily over a wide range by limiting the size of either the ultraviolet or fluorescent light beam with standard apertures.

Circular↗
USGS1950

An improved fluorimeter for the determination of uranium in fluoride melts

The Model R fluorimeter has been modified to increase its stability and sensitivity. The new instrument* is about ten times as sensitive as the original fluorimeter, but it can also be employed conveniently at a sensitivity level comparable to or less than that of the Model R fluorimeter. *The modified fluorimeter described here was developed in the latter half of 1948 and has since been in constant use in the laboratory for routine analysis. Although it is now being superseded to a large extent by a more recently developed transmission fluorimeter, the modified fluorimeter is a very useful tool for many types of analysis. (Fletcher, M. H., May, Irving, and Slavin, Morris, A transmission fluorimeter for use in the fluorimetric method of analysis for uranium: Trace Elements Investigations Report 104, August 1949.)

Trace Elements Investigations↗
USGS1950

The design of the Model V transmission fluorimeter

The transmission fluorimeter for the measurement of the fluorescence of uranium in fluoride melts is described. The instrument incorporates several improved features which have not been published previously. Unlike the earliest models, the design of the new fluorimeter, with its close machining of parts, reduces the possibility of light leakage and also increases considerably the ease with which the various components of the instrument may be assembled and adjusted. The Model V fluorimeter is a very rugged instrument with a compact arrangement of parts. It possess great flexibility so that various phototubes, measuring devices, light sources, and filter combinations may be used interchangeably. Detailed shop drawings are given for the construction of the fluorimeter.

Trace Elements Investigations↗