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Bureau of Mines / Minerals yearbook: Metals and minerals 1978-79
Year 1978-79, Volume 1 (1978-1979)

Kostick, Dennis S.; DeFilippo, Ronald J.
Fluorspar,   pp. 341-357 ff. PDF (1.9 MB)

Page 355

 The role of CFC's in the depletion of stratospheric ozone continued to be
a subject of controversy. One group at the Federal Republic of Germany's
Institute for Ecological Chemistry at Munich found that CFC's decompose in
the lower atmosphere.29 
 The effectiveness of satellite measurement of stratospheric ozone and aerosols
was a subject of a study commissioned by the National Aeronautics and Space
Administration.29 The Manufacturing Chemists Association set up a network
of four CFC monitoring stations located in Ireland, Barbados, American Samoa,
and Tasmania. Data from the stations is expected to help determine if there
is any accumulation or natural sinks for CFC's in the lower atmosphere.3°
 Some measurements have detected an increase in stratospheric ozone. It was
proposed that increased atmospheric carbon dioxide levels may be linked to
the increase in ozone.3' 
 A researcher at Rochester University determined that water supply fluoridation
may be a factor in the reduction of heart disease. This determination may
support the theory that fluoride inhibits calcification, which causes hardening
of the arteries around the heart.32 
 E. I. du Pont de Nemours & Co., Inc., and Imperial Chemical Industries,
Ltd., conducted further testing of CFC F22 after preliminary tests had indicated
the material was weakly tetratogenic in rats. Exposure to F22 at the Occupational
Safety and Health Administration maximum concentration standard of 1,000
parts per million was found to have no statistically significant ill effects.
Du Pont continued to recommend that use of F22 be limited until further long-term
tests are completed.~~ 
 A study of fluoride emissions from gypsum-disposal and cooling-water ponds
of phosphoric acid manufacturing plants was released. It was concluded that
the most promising method of fluoride emissions control was to recover H2SiF6
and segregate cooling-water from gypsum-pond waters.34 
 The National Institute for Dental Research recommended that children start
regular programs to rinse with fluoride preparations for tooth decay prevention.
A 3-year project using fluoride preparations and focusing on elementary school
children found that tooth decay could be reduced by 
an average of 35%35 
 A patent was granted for a method of detecting subsurface deposits of fluorspar.
The method uses a combination of magnetic and gravitational techniques.36
A patent was also granted for a new method of beneficiating fluorspar and
other nonsulfide ores by froth flotation. The collector used in the process
is a partial ester of polycarboxlic acid said to enhance recovery and at
the same time permit recycling of process streams.37 Another patent was granted
for a method using fluorine compounds to recover titania from ilmenite. The
ore is first digested with HF, and the solution is then treated with ammonium
fluoride and hydroxide in order to precipitate an iron-ammonium complex.38
A Canadian patent was awarded for a method of detecting fluorspar in an ore
or in rock samples. The chemical colorimetric test is particularly suitable
for diamond-drill cores.39 A history of development, present processes, and
uses for fluoroaromatics was discussed.~° 
 Apart from a growing use of SF6 as a dielectric, SF6 was noted for its utility
as a leak detector in water mains. The nontoxic, nonpolluting gas is injected
into the main at a concentration of about 6 parts per million. Shallow holes
about 6 inches deep are made along the pipeline route, and each one is checked
for the presence of SF6 gas with a commercially available detector. The use
of SF6 to replace tracer dyes for river monitoring studies was also contemplated~'
 An announcement was made that a 125ton-per day demonstration plant would
be constructed, using fluorocarbons as the liquid medium in a flotation process
to remove sulfur and other impurities from coal. The project was to be funded
by the American Electric Power Institute.~~ A multiclient study conducted
by Batelle Columbus Laboratories concluded that fluoroplastic-lined steel
products would soon find much wider application in the chemical process industries
because of the plastics' high heat stability and low reactivity. The fluoroplastics
can be applied directly to coil steel, making direct forming of a precoated
product possible.~3 
 Developments in fluorinated coatings for ships were reported. These new
coatings provided a tough, durable membrane and were heavily fluorinated,
highly crosslinked materials of the epoxy and polyuret 

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