Masters Theses

Abstract

"Pyrite (FeS2), cattierite (CoS2), and various transitional members of the solid solution compounds were prepared. The methods used are as follows:

First, sulfides of cobalt, iron, or cobalt-iron were obtained by precipitation from a mixture of the cobalt chloride and/or ferrous sulfate in an aqueous solution. The dried precipitates were then mixed with an equal weight amount of sulfur and placed into silica glass tubes. After evacuation, they were filled with hydrogen gas of 3/4 of atmospheric pressure and sealed. The samples were then heated up to 500°C (for FeS2), 650°C (for FeS2-CoS2), and 750°C (for CoS2) for 24 to 72 hours. Pyrite, solid solutions of FeS2-CoS2, and cattierite were then formed.

In addition, pyrite has also been synthesized by using the method of WOHLER (1836). This method is based on the direct reaction of S with Fe2O3 which are mixed in certain proportions and placed in an electric furnace at a constant temperature of 360°C. An amount of NH4Cl equal to that of Fe2O3 + S was also added to the mixture before heating. The time of heating was between 24 to 72 hours. The pyrite crystals so produced appeared as cubes, octahedra, pyritohedra and as their combinations.

The density of natural pyrite could be changed through mechanical grinding. The finer the sample was ground the lower the density was. Therefore, the ratio of Fe to S changed from 1:1.994 to 1:1.945. This was calculated from the equation: nM=n(A + xB) = NoVd, where n is the theoretical number of atoms per unit cell (=4), A and B are atomic weights of elements in solid solution, No is the Avogadro’s number, V is the volume of the unit cell, and d is the density. Or, the number of atoms per unit cell, varied from n’ = 3.995 to n’ = 3.941 assuming that molecular weight is exactly FeS2 (calculated from the same equation: n’ = VdNo/A).

Experiments on the detection of the decomposition of pyrites have also been made by using the X-ray diffraction method. The pyrites decomposed completely into pyrrhotite and sulfur at 625°C in a vacuum; however, the decomposition started well below 625°C e.g. at 400°C.

The average lattice parameter of synthetic pyrite (5.40762 kX at 25°C) was slightly higher than that of the natural pyrites (5.40651 kX at 25°C). Yet, the linear thermal expansion coefficients of synthetic pyrite (average = 7.26 x 10-6 deg-1) did not differ much from those of the natural ones (8.52 to 9.25 x 10-6 deg-1) in spite of the variable crystal habit and the diverse localities of occurrence of the natural pyrites (cubes, pyritohedra, and octahedra of pyrite from the U. S., and Peru were used).

The average lattice parameter of synthetic cattierite (CoS2) was 5.52508 kX at 25°C and the average linear thermal expansion coefficient was 13.76 x 10-6 deg-1.

The components FeS2 and CoS2 formed a complete series of solid solutions at 650°C and the lattice parameter changed along a straight line from that of FeS2 to that of CoS2."--Abstract, pages ii-iv.

Advisor(s)

Amstutz, G. C. (Gerhardt Christian), 1922-

Committee Member(s)

Straumanis, Martin E., 1898-1973
Lorey, G. Edwin
Schlechten, A. W.

Department(s)

Geosciences and Geological and Petroleum Engineering

Degree Name

M.S. in Geology

Publisher

Missouri School of Mines and Metallurgy

Publication Date

1962

Pagination

ix, 101 pages

Note about bibliography

Includes bibliographical references (pages 68-74).

Rights

© 1962 Samuel Chan, All rights reserved.

Document Type

Thesis - Open Access

File Type

text

Language

English

Subject Headings

Sulfide minerals -- Synthesis
Pyrites -- Synthesis
Cobalt alloys -- Synthesis
Sulfide minerals -- Analysis

Thesis Number

T 1414

Print OCLC #

5938361

Electronic OCLC #

987910890

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Geology Commons

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