INDUSTRIAL AND ENGINEERING CHEMISTRY
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pressure point on the phase diagram can be made to pass to a composition on the opposite side of this maximum point. The evaporation behavior of toluene-isopropanol mixtures illustrates a general behavior of constant-evaporating systems. In Figure 1 the variations in composition of the liquid plotted against duration of vaporizations are given for various toluene isopropanol mixtures. Compositions are expressed in terms of refractive index and may be estimated from the following: Mole % Toluene 0.0 7.36 15.16 23.46
A New Water-Soluble Nicotine Insecticide-
NICOTINE HUMATE
Refractive Mole % Refractive Mole % Refractive Toluene Toluene Index Index Index 1.378 32.2 1.423 74.2 1.471 1.389 41.7 1.434 82.9 1.483 1.400 51.7 1.446 100.0 1.496 1.411 62.6 1.458
For toluene-isopropanol mixtures, then, there is one mixture (C, Figure 1) which evaporates without change in composition (refractive index) a t 20” C., while every other mixture richer or poorer in toluene, becomes increasingly richer or poorer as the evaporation proceeds. In no case does a mixture of a given composition on the phase diagram so alter in composition as to be subsequently represented by a point on the opposite side of the maximum point. In terms of Figure 1 such an alteration would necessitate a change in refractive index from one side to the other of horizontal line C (the maximum pressure composition) on the graph. The authors have previously reported the experimental details and data for eight such systems ( B ) , all of which exhibit this general evaporation behavior. It may be said, then, that the second point of the Lewis, Squires, and Sanders assertions is not universally true. In regards to the third point-namely, the identity of the constanbboiling and the constant-evaporating mixtures-the authors are unable to cite a research specifically undertaken to establish such identity. Comparable data for the system toluene-ethanol are, however, available (6, IO) over the range 50” to 75” C. This comparison is shown in Table I1 and graphically in Figure 2. On the other hand, similar concordance cannot be established for benzene-methanol based on the published data (1, 3-6, 8).
WEIQHINGTHE INSECTICIDE FOR EXPERIMENTAL SPRAYING, KEARNEYSVILLE, W. VA.
TABLE 11. COMPARISON OF COMPOSITIONS OF CONSTANT-BOILINQ AND CONSTANT-EVAPORATING MIXTURESOF TOLUENE AND ETHANOL Temp. a
c.
75 70 65 60
ConstantConstantBoiling Evaporating Mole % toluene 18.0 18.0 18.5 18.7 19.5 19.5 20.0 20.0
Temp. o c .
55 50 25 0.5
L. N. MARKWOOD Bureau of Entomology and Plant Quarantine. U.S.Department of Agriculture, Washington, D. C.
’
Acknowledgment The authors are indebted to Ernest Robinson for the data represented in Figure 1.
Literature Cited (1) Hofmann, IND. ENG.CHEM.,24,135 (1932). (2) Hofmann and Reid, Ibid., 20,687 (1928). (3) Leoat. “L’azBotropisme,” 1st ed., p. 99,Henri Lamertin, Brussels, 1918. (4) Lee, J . Phys. Chem., 35,3558 (1931). ( 5 ) Lewis, Squires, and Sanders, IND. ENG.CHEM.,27, 1395 (1935). (6) Robinson, Wright, and Bennett, J . Phys. Chem., 36,658 (1932). (7) Roscoe and Dittmars, J . Chem. Soc., 12, 128 (1860). ( 8 ) Schmidt, 2.physik. Chem., 99,71 (1921). (9) Taylor, “A Treatise on PhyRical Chemistry,” 2nd ed., Vol. I, P. 523, New York, D.Van Nostrand Go., 1931. (10) Wright, J . Phys. Chem., 37,233 (1933). R E C ~ I V EFebruary D 13, 1936.
0
Constant- ConstantBoiling Evaporating Mole % toluene 20.5 20.7 21.5 21.5 .. 26.9 .. 36.8
The three concepts, expressed or implied by Lewis, Squires, and Sanders cannot, therefore, be universally true.
VOL. 28, NO. 6
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PREVIOUS paper1 the author described a process in which nicotine and peat are brought together to form a waterinsoluble product named ‘ ‘nicotine peat ,” The liquid separated from nicotine peat also contains nicotine, not as the free base but in combination with humic acid derived from the peat. This aqueous solution can be treated with alkali and the nicotine recovered by distillation, but since the compound in solution, nicotine humate, may have a usefulness of its own, it has been recovered unchanged by evaporating the water. Wcotine peat and nicotine humate are thus companion products formed in a single reaction. Nicotine humate is a black product, soluble in water, forming what is‘ undoubtedly a colloidal solution. As obtained by evaporation it has a high luster, which gives it the appearance of a black crystalline substance. Actually, however, it is amorphous. Its aqueous solution is slightly acid to litmus. The addition of a strong mineral acid, such as hydrochloric, 1
IND. ENQ CHEM., 28561, (1936)
JUISE, 1936
INDUSTRIAL AND ENGINEERIKG CHEMISTRY
precipitates humic acid, leaving the corresponding nicotine salt in solution. A weak acid, such as acetic, does not produce a precipitate of humic acid in dilute solutions, although it will do so in stronger solutions. The action of alkalies is the same as on all nicotine salts-viz., free nicotine is formed. The chief commercial nicotine insecticide is nicotine sulfate. It appears on the market as an aqueous solution containing 40 per cent of nicotine. Nicotine humate should be equivalent insecticidally to the sulfate. It possesses the advantage, moreover, of being a solid and thus can be handled and shipped in a dry state. If the manufacture of nicotine peat becomes a reality, the recovery and use of nicotine humate as B valuable by-product will be a logical consequence.
Procedure Since the operations involved in making nicotine peat have already been described,l it is sufficient to state that the black liquid formed in the reaction can be evaporated to dryness and the nicotine humate obtained as a dry residue. Direct filtration of the reaction mixture, a t least throughapaperfilter; is difficult because the filter soon becomes clogged. Separation is accomplished best by centrifuging or by settling. A suitable procedure is to dilute the mixture with 2 or 3volumes of water, stir well, let stand for 24 to 48 hours, and then siphon off the supernatant liquid. After this operation has been repeated four or five times, a t which stage the liquid is still colored and contains an appreciable quantity of nicotine, the remainder of the nicotine humate can be successfully washed out on the filter. Washing is stopped when only a slight positive test for nicotine is obtained (as shown by only a slight opalescence with silicotungstic acid). The temperature of evaporation is important. If conducted on a steam bath, the residue is partly decomposed. Some nicotine is lost and the liberated humic acid prevents the material from giving a clear solution. Furthermore, the deposit adheres tightly to the evaporating dish and can be scraped out only with difficulty. When evaporation is conducted a t a reduced temperature, approximately 60" C., these difficulties vanish. The material is easily removed from the dish (in fact, it flakes off in thin layers), the aqueous solution is clear, and the nicotine content is slightly higher. The material can be readily pulverized to any desired fineness.
Results Data obtained from various peats are presented in Table I. The nicotine content of the nicotine humate ranges from 28 to 34 per cent, depending chiefly on the type of humic mate-
Nicotine peat and nicotine humate are companion products formed in the reaction of nicotine and peat. Nicotine humate is found in the aqueous portion and may be recovered in the form of a black solid by evaporating the water. I t is a stable product giving a clear solution in water. It contains from 28 to 34 per cent of nicotine, depending chiefly on the type of peat from which it is made. The yield is a function of the type of peat and its preliminary treatment and the ratio of peat to nicotine. The product has insecticidal possibilities similar to those of commercial nicotine sulfate.
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rial employed. Probably in most cases the nicotine content of a given peat is not significantly changed by preliminary acid treatment. The New Jersey and North Carolina peats are in this class, and the Alaska peat shows only a small difference. The German moss peat, however, exhibits more than a 4 per cent difference. TABLE I. NICOTIXE CONTENT AND YIELD OF NICOTINE HUMATE OBTAINEDFROM VARIOUSPEATS (Twenty grams of peat used in each test) Nicotine -Nicotine HumateYield Nicotine content Used Crams Grams Per aent S e w Jersey reed: Untreated 4 0.8 33.9 3.6 34.1 Acid-treated 11.5 2.8 33 5 German mom: 4 2 0 33.8 Untreated Acid-treated 4 2.0 29.7 North Carolina sedge: Untreated 5.3 28.4 5.4 29.1 Acid-treated Alaska sedge: Untreated 2.0 32.3 Acid-treated 3.2 30.2 Peat
The yield depends on the variety of humic material, on whether or not it was pretreated with acid, and also on the relative quantity of nicotine employed in the reaction. Differences in yield, as related to acid pretreatment, are greatest for theneutral or alkaline peats, suchas New Jersey peat, and negligible for acid types, such as German moss and North Carolina peat. The North Carolina peat gives the greatest yield of nicotine humate. Therefore, if we were interested in that commodity alone, that peat would be the type to select. The nicotine peat produced from it, however, is of a low grade, carrying only about 3.3 per cent nicotine for either untreated or acid-treated products, and hence the North Carolina peat would probably not be selected for commercial use. In order not to waste nicotine, which is costly, it is advisable to use no more nicotine than is equivalent to the acid constituents of the peat. If the mixture after reaction is acid, this condition is satisfied. It is believed that the ideal amount of nicotine to be used is such that the mixture is approximately neutral, which results in no waste of nicotine and gives the maximum yield of humate.
Alternative Method It is also possible to prepare nicotine humate by a modified method using precipitated humic acid instead of peat. The following experiment indicates the procedure: A quantity of German moss peat was digested on the steam bath with a 2 per cent sodium carbonate solution. The filtered liquid was acidified with hydrochloric acid, and the humic acid precipitate was thoroughly washed. To an aqueous suspension of the humic acid was added an aqueous solution of nicotine in slight excess. On evaporation to dryness the black residue of nicotine humate was deposited. This product contained 28.6 per cent nicotine, a value not significantly different from 29.7 per cent recorded for acid-treated German moss in Table I. Letters patent covering this product and the process of making it have been applied for under the Act of March 3, 1883, as amended. RECEIVrD
April 14, 1986.
