Abstract-Palygorskite and sepiolite were digested with large excesses of hydrochloric acid at constant temperature for various periods of time. The reaction was found to be of first order with respect to the magnesium, aluminum and iron components in the clay and also with respect to hydrochloric acid concentration.The reaction rate constant for Mg is larger than for Fe, which is larger than for A|. Approximately one-third of the octahedral-type cations are extraneous, suggesting that only three of the five octahedral positions are filled. The reaction rate constant of Mg in sepiolite is about 240 times that for palygorskite. This may be an indication that sepiolite is less stable to chemical weathering than palygorskite.The activation energies for Mg, AI and Fe in palygorskite were found to be the same and equal to about 18.4 kcal per mole.Treatment of partially acid-digested palygorskite with magnesium ions under alkaline conditions resulted in an increase in the X-ray intensity of the 10.5 A spacing, suggesting some of the palygorskite was reconstituted.

An improved equation of Chrastil's model was developed for predicting the solubility of vegetable oil (c, gram of oil/liter of C02) in compressed C02 as a function of temperature (T) and density (p), which accounts for variations of the solute's heat of vaporization with temperature: c = exp(40.361 -18708/T + 2186840/T2)p10•124 ± 2.7. The equation was validated for absolute temperatures from 293 to 353 K and pressures between 150 and 880 atm and adequately predicted solubilities under 100 g/L within the region suggested for commercial supercritical fluid extraction of food components. Supercritical fluid extraction (SEE) has been proposedas a viable alternative to current extraction processes used by the vegetable oil industry. Carbon dioxide (C02) is an