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Thiocyanate complexes of osmium

Author

Craig Albert Townsend Jr., University of the Pacific

Date of Award

1953

Document Type

Thesis

Degree Name

Master of Arts (M.A.)

Department

Chemistry

First Advisor

Emerson G. Cobb

First Committee Member

Don DeVault

Abstract

Osmium is a hard grey brittle metal which scratches glass. It has a melting point of 2700[degree]C, and a specific gravity of 22.4, which is greater than any other known substance. The grey color of osmium resembles the grey color of iron and ruthenium. Osmium was discovered in 1803 by Tennant in the insoluble residue remaining after treating an alloy of the platinum metals with acid.

Osmium occurs in nature alloyed with the other metals of the platinum group. One type of alloy includes all six of the of the platinum metals, osmium, iridium, platinum, ruthernium, rhodium and palladium. Osmium also occurs in an alloy of osmium and iridium called osmiridium. These alloys are usually recovered by placer mining methods. Canada, Russia, Colombia, South Africa and the United States are the worlds producers of platinum metals. The beds of Alaskan rivers contain platinum metals.

Osmium has limited uses due in part to scarcity. Its cost is approximately fifty dollars per ounce. Haber found that osmium metal catalyzes the synthesis of ammonia from the elements. Other investigators have ranked osmium first in catalytic powers among the platinum metals. Osmium alloys are used for bearings in place of jewels in precision instruments because of their resistance to wear. Osmium alloys are also used in pen points because of their resistance to wear and corrosion Osmium tetroxide finds use as a catalyst in inorganic and organic reactions. It is employed as a catalyst in the quantitative determination of arsenic in which arsenite is titrated with ceric sulfate. Osmium tetroxide catalyzes the action of potassium permanganate on maleic acid to form meso-tartaric acid; and also catalyzes the additions of hydrogen peroxide to other ethelenic compounds to form glycols. Osmium tetroxide is used to develop fresh glycols. Osmium tetroxide is used to develop fresh finger prints. It also finds use as a hardening and staining agent in making sections for study under the microscope in biological work. Many problems were encountered in attacking the structure of the osmium thiocyanate complex. Preliminary investigations showed that the red complex could be prepared by the direct action of osmium tetroxide on solutions of sodium thiocyanate in perchloric acid. Complex colors developed in great excess of thiocyanate showed no fading over a period of a week. The complex was found to follow Beers law (See figure 1). Sulfate ions appeared as a by product of the reaction, indicating a reduction of the osmium to a lower oxidation state. The speed of the reaction appeared to be dependent on on CNS concentration. At high CNS concentrations, good colors were developed, but at lower concentrations the colors were obscured by the appearance of a dark precipitate of a colloidal nature.

Pages

30

Recommended Citation

Townsend, Craig Albert Jr.. (1953). Thiocyanate complexes of osmium. University of the Pacific, Thesis. https://scholarlycommons.pacific.edu/uop_etds/343