INDUSTRIAL AND ENGINEERING CHEMISTRY
360
Extraction of Acetic Acid from Isoamyl Alcohol with Water Hertz and Fischer (3) determined the distribution constant for this system a t 20" C., and obtained a value of 0.923. I n this study the constant, uncorrected for dissociation, a t 25" C. was found to be 0.936. Employed in the calculations for the purpose a t hand the value 1/0.936, or 1.07, was used. Analyses of the two layers for acetic acid content were made by titrating with standard sodium hydroxide solution. Figure 4 shows the five points obtained in this case. All experimental points except for n = 10 are very near the theoretical curve. Duplicate runs for n = 10 yielded points, both of which fall slightly below the curve. It should be pointed out that this case is different from that shown in Figure 3 where the experimental points fell progressively further below the curve as n took on increasing values. In
VOL. 8, NO. 5
the present case, although, because of increased dissociation of acetic acid in the aqueous phase with greater dilution, more efficient extraction would be expected as n is increased, nevertheless the dissociation of acetic acid for concentrations prevailing when n = 1 and when n = 10 is of the same order of magnitude; only when n takes on high values would dissociation prove an important factor.
Literature Cited Abegg, Fox, and Hertz, 2. anorg. Chem., 35, 129 (1903). Griffin, IND.ENG.CHEM., Anal. Ed., 6,40 (1934). Hertz and Fischer, Ber., 37,4746 (1904). Jakowkin, 2. physik. Chem., 18, 585 (1895). (5) Landau, Ibid., 73,200 (1910). ( 6 ) Taylor, "Treatise on Physical Chemistry," p. 478, New York, D. Van Nostrand Co., 1931.
(1) (2) (3) (4)
RECEIVBID June 5, 1936.
Solubility of Naringin in Water GEORGE N. PULLEY, Bureau of Chemistry and Soils, U. S. Citrus Products Station, Winter Haven, Fla.
T
H E possibility of utilizing grapefruit residue for the production of naringin and its hydrolytic products, together with the fact that there is a limited commerical production of naringin at the present time, has shown the desirability of determining the solubility of naringin in water at various temperatures. Naringin (C27HS2014.2H20) was discovered by DeVry (2) in the flowers of grapefruit trees growing in Java. Will (6, 7 , 8), Zoller (Q),and Asahina and Inubuse (I) have conducted studies to determine its properties. Its increased solubility in hot water or juice has been noted by Fellers (S),and Segal and de Kiewiet (5) in technological studies on grapefruit products. The content of naringin in both peel and juice appears to diminish as the fruit matures. It is soluble in alcohol, acetone, and water. When crystallized from these solvents and dried a t 110" C. it melts a t 171" C. When crystallized from water it has an additional 6 molecules of water and melts a t 83" C. The bitter taste of naringin is pronounced: a water solution containing one part in ten thousand has a distinctly bitter taste. The naringin used in these experiments was made from grapefruit peel, purified by t h e method outlined by Poore (4) and dried at 110°C.; themeltingpoint was 171°C. (uncor.).
TEMPERATURC ' C
FIGURE1
The solubility of narin in was determine$ by adding an excess of the purified material t o 150 CC. of distilled water containedin aflask which was closed with a rubber stopper and immersed in a constant-temperature water b a t h . T h e flask was left in the bath 2 hours and was shaken every 15 minutes. At the end of 2 hours the solution in the flask was rapidly filtered, using a
water-jacketed funnel. A measured volume of the clear filtrate was transferred to a weighed evaporating dish and evaporated to dryness over a steam bath, then dried at 110" C., cooled, and weighed. The amount of naringin dissolved per 1000 cc. was calculated from the average of two determinations. The solubility at 6' C. was determined by placing the flasks in an electric refrigerator, while the solubility at 20" C. was determined in an ice-cooled box. The variation in the temperature at these two points was greater than at the higher temperatures, but, since the increase in solubility of naringin between 6" and 35' is so small, fluctuations in temperatures at 6" and 20" C. would have no significant effect upon the solubility value. Solubilities at other temperatures were carried out in a water bath, the temerature of which was controlled by means of a gas thermoregufator. The water in the bath was kept in constant motion by means of compressed air. The data given in Table I and Figure 1 show that up to 45" C. the increase in solubility with increase in temperature is not pronounced. From 45" C. to the melting point (83" C.) the solubility increases rapidly with increase in temperature. TABLEI. SOLUBILITY OF NARINQIN IN WATER Solubility in Water U . / l O O O cc. 6 0.17 20 0.50 35 0.79 1.96 45 7.16 55 42.21 65 76 108.24 The decreased solubility of naringin a t low temperatures may a t times cause the precipitation of this substance in canned grapefruit juice and sections as has been pointed out by Fellers and by Segal and de Kiewiet (6), This 'is especially true if the juice or sections have been prepared from immature or frozen fruit. I n the case of canned juice the glucoside generally settles t o the bottom of the container as a yellow sludge. Sections may show light yellow spots, which macroscopically have the appearance of mold. At times the juice has a milky appearance due t o minute crystals of naringin. Temperature of Water
c.
Literature Cited (1) Asahina, Y., and Inubuse, M., J . P h a r m . Sac. J a p a n , 49, 1928-35 (1929). (2) DeVry, Jahresber. Ph,armacog., 1886, 132. (3) Fellers, C. R., Canner, 69, No. 18, 11-12 (1929). (4) Poore, H. D., IWD. ENG.CHEM., 26, 637-9 (1934). (5) Segal, B., and de Kiewiet, T., J . South African Chem. I n s t . , 14, 43 (1931). (6) Will, W., Ber., 18, 1311-25 (1885). (7) Ibid., 20, 294-304 (1887). (8) Ibid., 20, 1186 (1887). ENQ.CHEM.,17, 1065 (1925). (9) Zoller, H. F., IWD. RECEIVED June 13, 1936.
Food Research Division Contribution No. 288
