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)
FLUORSPAR TECHNOLOGY 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
http://rightsstatements.org/vocab/NoC-US/1.0/| As a work of the United States government, this material is in the public domain.| For information on re-use see: http://digital.library.wisc.edu/1711.dl/Copyright