February, 1942
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
114) Garvey, B. S., Jr., Alexander, C. H., Kung, F. E., and Henderson, D. E., IND. ENG.CHEM.,33, 1060 (1941). (16) Koch, 2. V e r . deut. Ing., 80, 963 (1936); Rubber Chem. Tech., 10, 17 (1937). (16) Konrad, E., and Tschunkur, E., U. S. Patent 1,973,000 (1934); German Patent 658,172 (1938). (17) Patrick, J. C., Trans. Faraday SOC.,32, 347 (1936); Rubber Chern. Tech., 9, 373 (1936). (18) Patrick, J. C., U. 9. Patent 1,890,191 (1932). (19) Schade, J. W., Rubber Age (N. Y . ) ,48, 387 (1941). (20) Sebrell, L. B., and Dinsmore, R. P., India Rubber W o r l d , 103, 37 (March, 1941). (21) Semon, W. L., U. S. Patent 1,929,453 (1933). (21A) Sparks, W. J., Lightbown, I. E., Turner, L. B., Frolich, P. K., and Klebsattel, C. A,, IND.ENQ.CHEM.,32, 731-6 (1940); Rubber Chem. Tech., 13,521 (1940).
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Stocklein, P., T r a n s . Inst. Rubber Ind., 15, 51 (1939). Street, J. M., and Ebert, H. L., Rubber Chem. Tech., 14, 211 (1941). Thomas, R. M., Lightborn, I. E., Sparks, W. J., Frolich, P. K., and Murphree, E. V., IND.ENG.CHEM.,32, 10, 1282-92 (1940); Rubber Chem. Tech., 14, 177 (1941). Tschunkur, E., and Bock, W., U. S. Patent 1,938,731 (1933); German Patent 570,980 (1933). Whitby, G. S.,and Katz, M., IND. ENC. CHEM.,25, 1204, 1338 (1933); Rubber Chern. Tech., 7,40 (1934). Williams, C. G., Proc. R o y . SOC. (London), 10, 516 (1860). Wolf, Ralph, and Wolf, Howard, "Rubber-A Story of Glory and Greed", p. 375, New York, Covioi & Friede, 1936. Wood, L. A,, Natl. Bur. Standards, C ~ T CC-427 . (June, 1940); Rubber Chem. Tech., 13, 861 (1940).
Azeotropism in the System Nicotine-Water Separation of Nicotine from Related Alkaloids by Aqueous Distillation C. R. SMITH' Bureau of Entomology and Plant Quarantine, United States Department of Agriculture, Washington, D. C
ICOTINE is completely miscible with water below 60' and above 210" C. At 100" nicotine in total concentrations between 6 and 80 per cent forms two layers consisting of nicotine dissolved in water and water dissolved in nicotine. The composition of each layer is invariable, but the proportionate volumes of the layers vary with the concentration. The boiling point of such mixtures is that ofithe phase containing nicotine dissolved in water and is constant, since the composition of each layer is constant. I n concentrations below 6 per cent nicotine is completely miscible with water a t 100' C.; above this concentration the nicotine in the saturated water layer has a fixed value of 6 per cent. The author has studied the distillation of aqueous nicotine solutions from simple stills and from stills connected with fractionating columns of various types. He found that nicotine in a concentration of 2.5 grams per 100 cc. under atmospheric pressure forms an azeotropic mixture which distills unchanged with any type of distillation. At this concentration nicotine lowers the boiling point of water slightly (about 0.012' C.), I n proceeding from pure water, there is a slight increase of total vapor pressure until a concentration of 2.5 grams of nicotine per 100 cc. is reached, and then a decrease up to 6 grams where i t becomes constant. Judging from the results of distillation experiments, the vapor pressure-concentration curve deflects more sharply in passing from 6 to 2.5 per cent than it inflects between 2.5 per cent and pure water, which means that the minimum boiling point mixture is more readily reached in passing from 6 to 2.5 per cent than from lower concentrations.
N
1 Present address, Eastern Regional Research Laboratory, U. 8. Department of Agriculture, Wyndmoor, Penna.
It is generally accepted that the peculiar solubility curve of nicotine is connected with the formation of hydrates. Below 60 C. nicotine exists largely in a hydrated form soluble in all proportions in water; above 60' we deal with free nicotine which has a limited solubility. I n extracting nicotine from aqueous solutions with immiscible solvents, we are removing the nonhydrated nicotine until equilibrium is established between it, the two solvents, and the hydrated form. The primary object of this investigation was to study means of separating nicotine from such associated alkaloids as anabasine, nornicotine, and others that may be found in the various species of Nicotiana now being studied. The existence of a nicotine-water azeotropic mixture has been of great assistance. Neither nornicotine nor anabasine forms such a mixture, for when their solutions in water are repeatedly fractionated through efficient fractionating columns, a distillate of pure water may be obtained. A complete separation of nicotine can therefore be made from either of these two alkaloids, although they are slightly volatile with water vapor in simple stills. In the usual analytical procedure for determining nicotine, involving distillation from strongly alkaline solutions through apparatus with little fractionating effect, associated alkaloids, if present, may be completely removed with the nicotine in spite of their lesser volatility. I n the distillation of dilute solutions of nicotine with alkali, nicotine is more efficiently concentrated by slow distillation through a good fractionating column when the minimum boiling point concentration is approximately obtained; with rapid steam distillation as usually practiced, more water is distilled than is necessary to remove the nicotine. The associated alkaloids always present in tobacco are thereby also
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INDUSTRIAL AND ENGINEERING CHEMISTRY
252
TABLE I. DISTILLATION OF AQUEOUS NJCOTINE SOLUTIONS 7 -
Concentration. Grams per 100 Ml.v
Fraction (20 CC.)
Initial
Final
1st 2nd 3rd 4th 5th
0,507 0.473 0.431 0.387 0.345
0.473 0.431 0.387 0.345 0.293
1st 2nd 3rd 4th 5th
1.014 0.960 0.904 0.846 0.781
0.960 0.904 0.846
1st
2.028 1.999 1.973 1.942 1.910
1.999 1.973 1.942 1.910 1.869
dv.C’
Dist. C ”
*C” = c
0.818 0. 805 0.737 0.640 0.575
1.67 1.78 1.80 1.75 1.80
1.497 0.409 1.312 1.241 1.144
1.52 1.51 1.50 1.53 1,54
2.284 2.219 2.177 2.138 2.122
1.13 1.12 1.11 1.11 1.12
Experiment I 0.490 0.452 0.409 0.366 0.319
Experiment I1
0.781 0.708
0.987 0.932 0.876 0.813 0.744
Experiment 111 2nd 3rd 4th 5th
2.014 1.986 1.957 1.926 1.889
Experiment IV 1st 2nd 3rd 4th
5th
1st 2nd 3rd 4th 5th
3.042 3.068 3.113 3.169 3.236
3.068 3.113 3.169 3.236 3.331
3.055 3.091 3.141 3.202 3.283
2.754 2.747 2.744 2.754 2.770
0.901 0.888 0.874 0.860 0,844
4.056 4.162 4.293 4,461 4.680
Experiment V 4.162 4.109 4.293 4.227 4.461 4.377 4.680 4.571 4.978 4.829
3.110 3.110 3.116 3.143 3.191
0.736 0.712 0.687 0.661
3.208 3.305 3.337 3.337 3.451
0.620 0.613 0.587 0.552 0.528
0.757
pressures recorded by a sensitive aneroid barometer. When readings showing marked atmospheric changes were discarded, it was found that the lowering amounted to only 0.012O C. It was thought unnecessary to make the determinations a t other concentrations because of the slight lowering and the uncertainty of the nicotine-water concentration on the bulb of the thermometer. SEPARATIOK OF KICOTINE FROM NORNICOTINE AND ANABASINE. When an aqueous solution of either nornicotine OP anabasine is fractionated through the same bulb-type fractionating column, the ratio C”/C’ is much less than in the case of nicotine. TF7ith a more efficient column (Widmer’s) the ratio was about 1 / 2 0 . The results in Table I1 were obtained with the same column used in experiments I to VI.
TABLE 11. DISTILLATION OF AQUEOUSANABASINESOLUTION^ (INITIAL VOLUME200 Cc.) c -
Fraction (25 Co.) 1st 2nd 3rd 4th 5th 6th
Concentration, Grams per 100 . .M l
Initial 1.00 1.14 1.30 1.53 1.89 2.46
Final 1.14 1.30 1.53 1.89 2.46 3.60
bv. C’ 1.07 1.22 1.41 1.71 2.17 3.03
Dist. C” 0.103 0.103 0.114 0.130 0.154 0.174
C”
B
0.096 0.084 0.081 0.076 0.071 0.057
Experiment VI 1st 2nd 3rd 4th 5th
a
5.069 5.266 5.523 5.832 6,250 Two layers formed.
5.266 5.523 5.832 6.260 6.810
5.168 5.394 5.677 6.041a 6.530Q
largely removed by steam distillation. The higher results obtained by this procedure are therefore due in part to the less volatile alkaloids.
Experimental Before the existence of an azeotropic mixture had been determined, a series of distillations was made from a six-bulb 13-cm. still head. The figures representing concentrations in still and distillate were substituted in the equation,
It will be seen later that C is not a constant but varies in a way to be expected because of the existence of the azeotropic mixture containing 2.5 grams of nicotine per 100 cc. DISTILLATION OF AQUEOUSNICOTINESOLUTIONS. 200 cc. of solution were distilled through the column, five fractions of 20 cc. each were collected, and the nicotine was determined by titration. The distillations were conducted as uniformly as possible, with the results given in Table I. The results indicate that C”/C’ will be unity between 2.028 and 3.042 grams per 100 cc. A series of distillations with concentrations between these amounts showed that a concentration of about 2.5 grams per 100 cc. gives the unity ratio and therefore represents a mixture with minimum boiling point. BOILINGPOINTDETERMINATIONS. The boiling point of the mixture containing 2.5 grams of nicotine in 100 cc. of water was compared with that of water by means of a Bcckmann thermometer. The difference was so slight that it was necessary to make a large number of readings a t atmospheric
Nicotine, Nornicotine, and Anabasine The quantitative separation of nicotine from nornicotine and anabasine singly and in mixtures containing both is shown in Table 111. The method of procedure consisted in distilling first the mixed alkaloids from 125 ml. of water solution through the TVidmer column to a low volume (about 15 ml.), adding 60 ml. of water containing 2 grams of sodium chloride, and continuing again to a volume of 15 ml. The combined distillate was titrated and calculated as nicotine, but represents all the nicotine with some of the accompanying alkaloid or alkaloids. This result is recorded as distillation I. The titrated distillate was made alkaline with a slight excess of standard alkali to neutralize the standard acid, and the distillations were repeated as before but without the addition of sodium chloride. The combined distillate was titrated, and the calculated nicotine is given as distillation 11. The results indicate a satisfactory separation was made.
TABLE 111. NICOTINE FROM ANABASINE AND NO~YICOTINE Anabasine, Nornicotine, Grams Gram 1.00 None 2.00 None 1.00 0.248 1.00 0.496 2.00 0.496 None 0.498 None 1.000 0.60 0.496 2.00 0.496
Nicotine, Gram 0.080 0.127 0.127 0.127 0.064 0.127 0.254 0.381 0.508
G r a m h-icotine Found in Distn. I I1 0.100 0.078 0.148 0.129 0.154 0.131 0.168 0.131 0.078 0.066 0.152 0.126 0.289 0.260 0.412 0.378 0.542 0.521
of T eory 97 102 103 103 103 99 102 99 103
Conclusions Nicotine forms an azeotropic mixture with water in a concentration of 2.5 grams per 100 ml. This property is used in separating it from either nornicotine or anabasine, or both.
