By in the literature that showed the boiling point for tetrafluoromethane to be high compared to those for other fluorinated compounds, The attention of Midgley and his associates was drawn to organic fluorides.
Subsequent of the antimony trifluoride, used to prepare the dichlorodifluoromethane from tetrachloride, showed that four of the five bottles available at the time contained water.
Commercial CFC production began with R-12 in early 1931, R-11 in 1932, R-114 in 1933, and R-113 1934 the first hydrochlorofluorocarbon refrigerant, R-22, was produced in 1936.
Close to half century passed between the introduction of CFCs and recognition of their harm to the environment when released, specifically depletion of stratospheric ozone and global warming as greenhouse gases.
tenet of toxicology, attributed to Paracelsus in the century, is dosis solo facit venenum, i.e., the dose makes the poison.
The difference between those regarded in some cases, the duration or repetition of exposures.
This increased reactivity is desired to reduce longevity, and thereby to reduce the fraction of emissions that reaches the stratospheric ozone layer or that persists in the atmosphere as greenhouse gas.
As examples, most CFCs are very in the atmosphere, generally less stable have comparable or toxicity than HCFCs or HFCs...
These limits therefore define the range of concentrations in which the substance is in air and establish guidelines for safe handling, specifically in assessing ventilation requirements for the handling of gases and vapors..
The table below summarizes the safety classifications from American Society of Heating, Refrigerating and Air-Conditioning Engineers Standard 34...
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