Discovery of SCFs and their Use as Solvents

The interest in SFRs has seen a tremendous increase over the last few years, because the special properties of SCFs make them particularly attractive solvents for modem synthetic chemistry. We should be aware of the fact, however, that the idea of using SCFs as reaction media has been emerging ever since the discovery of this peculiar state of matter early in the nineteenth century by Baron Charles Cagniard de LaTour, an experimental physicist in France [67]. 

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I introduced into a small Papin s digester, built from the end of a thick-walled gun barrel, a certain quantity of alcohol at 36 degrees and a marble or sphere of flint the liquid occupied nearly a third of the interior capacity of the apparatus. Having observed the kind of noise that the marble produced upon my making it roll in the barrel at first cold, and then heated little by little over a fire, I arrived at a point where the marble seemed to bounce at each collision, as if the liquid no longer existed inside the barrel [69]. 

The liquid, after approaching double its original volume, completely disappeared, and was converted into a vapor so transparent that the tube appeared entirely empty [70]. 

He refined his methods to allow for the determination of critical temperatures and pressures [71]. His values for diethyl ether and carbon disulfide are within 15 °C and 4 W of the values accepted today. 

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