Refrigerant History                                                                                             

The first practical refrigerating machine was built by Jacob Perkins in 1834; it used ether in a vapor compression cycle. The first absorption machine was developed by Edmond Carré in 1850, using water and sulfuric acid. His brother, Ferdinand Carré, demonstrated an ammonia/water refrigeration machine in 1859.[1]

A mixture called chemogene (consisting of petrol ether and naphtha) was patented as a refrigerant for vapor compression systems in 1866. Carbon dioxide was introduced as a refrigerant in the same year.[1-3]

Ammonia was first used in vapor compression systems in 1873, sulfur dioxide and methyl ether in 1875, and methyl chloride in 1878. Dichloroethene (dilene) was used in Willis Carrier's first centrifugal compressors, and was replaced with methylene chloride in 1926. [1-3]

Nearly all of the early refrigerants were flammable, toxic or both, and some also were highly reactive. Accidents were common.

The task of finding a nonflammable refrigerant with good stability was given to Thomas Midgley in 1926. He already had established himself by finding tetraethyl lead, to improve the octane rating of gasoline.

With his associates Henne and McNary, Midgley observed that the refrigerants then in use comprised relatively few chemical elements, clustered in an intersecting row and column of the periodic table of elements. The element at the intersection was fluorine, known to be toxic by itself. However, Midgley and his collaborators felt that compounds containing it should be both nontoxic and nonflammable.[4]

Their attention was drawn to organic fluorides by an error in the literature. It showed the boiling point for tetrafluoromethane (carbon tetrafluoride) to be high compared to those for other fluorinated compounds. The correct boiling temperature subsequently was found to be much lower. Nevertheless, the incorrect value was in the range sought and led to evaluation of organic fluorides as candidates.[5]

The shorthand convention later introduced to simplify identification of the organic fluorides, for a systematic search, is used today as the numbering system for refrigerants. The number designations unambiguously indicate both the chemical compositions and structures.

Within three days of starting, Midgley and his collaborators had identified and synthesized dichlorodifluoromethane, now known as R- 12.[4]

The first toxicity test was performed by exposing a guinea pig to the new compound. Surprisingly, the animal was completely unaffected, but it died when the test was repeated with another sample.

Subsequent examination of the antimony trifluoride (used to prepare the dichlorodifluoromethane from carbon tetrachloride) showed that four of the five bottles available at the time contained water. This contaminant forms phosgene (COCl2) during the reaction of antimony trifluoride with carbon tetrachloride. Had the initial test used one of the other samples, the discovery of organic fluoride refrigerants might well have been delayed for years.[2]

The development of fluorocarbon refrigerants was announced in April 1930. [5] To demonstrate the safety of the new compounds, at a meeting of the American Chemical Society, Midgley inhaled R-12 and blew out a candle with it. [6] While this demonstration was dramatic, it would be a clear violation of safe handling practices today.