NICOTINE PEAT A New Insoluble Nicotine Insecticide
(Above) EXPERIMENTAL SPRAYINGOF APPLE TREESAT
KEARNEYSVILLE, W. VA. (Right)FILLING THE SPRAYTANKFROM WATERTANKS IN THE REAR,FOR EXPERIMENTAL SPRAYING AT KEARNEYSVILLE.
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HE desirability of having available waterinsoluble nicotine products for insect control has recently been recognized and has stimulated research in that direction. For many years nicotine has been used as an insecticide in the free state or combined with sulfuric acid, but these materials are watersoluble and are used principally against the sucking ‘insects. If it becomes possible to develop a water-insoluble nicotine preparation of satisfactory toxicity, such a product will be peat, for which the designation “nicotine peat” is proposed. adaptable for the control of certain chewing insects. It might Peat is an organic type of soil which is widely distributed. also displace the hazardous inorganic insecticides such as Its chemistry is imperfectly understood even after many years those containing lead, arsenic, and fluorine. of investigation. An important ingredient is a group of acidic Recently two such nicotine insecticides were developed substances known collectively as “humic acid,” the constituand subjected to entomological tests, chiefly against the tion of which has not been established. This humic acid is codling moth, for which the standard control material is combined more or less, according to environmental conditions, lead arsenate. These products are nicotine tannate (3) and with basic elements, chieflv calnicotine bentonite ( 5 ) . cium, magnesium, iron, and aluA third insoluble n i c o t i n e L.N. MARKWOOD minum, thus giving peats of preparation is here presented for Bureau of Entomology and Plant Quarantine, acidity ranging from a p H of the first time. This is thereaction product of n i c o t i n e and u.s. Department of Agriculture, Washington, D. C. less than 4 to a p H of 7 or more.
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A water-insoluble insecticide can be
Peats vary in their capacity for holding nicotine. The highly acid peats combine with a greater amount of nicotine than the less acid or neutral peats. When peat is first treated with acids to remove inorganic basic constituents (calcium, magnesium, iron, aluminum, etc.) the nicotine content is increased, and the proportion of soluble nicotine is reduced. The peats that are benefited most by the acid treatment are those of least natural acidity.
formed by the reaction of nicotine and peat in aqueous solution. A study of the factors involved showed that the nicotine content of the product is not greatly affected by the concentration of nicotine, the degree of dilution, or the ratio of peat to nicotine. The coarser particles of peat are combined with m o r e nicotine than the finer ones. The presence of acid in the reaction reduces the nicotine content of the product. 561
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INDUSTRIAL AND ENGINEERING CHEMISTRY
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3' IL IL PERCENT NICOTINE IN PEAT (UNTREATED).ORGANIC BASIS
1. RELATIONBETWEEN THE ACIDITYOF A PEATAND THE NICOTINE CONTENT (ORGANIC BASIS) O F NICOTINE PEATMADE FROM IT
FIGURE
It is due to the presence of free acid that peat is able to combine with nicotine, a fairly strong organic base. Scholl and Davis (4) showed that peat combines with liquid (anhydrous) ammonia a t high temperatures and pressures to form a product in which the added nitrogen is largely insoluble in water and is no longer in the ammoniacal form. Feustel and Byers ( 2 ) , who worked with peat and aqueous ammonia solutions a t 150" C. under slight pressure, also found that there was combination between the two, the added nitrogen being chiefly nonammoniacsl but soluble. The chemical natures of ammonia and nicotine are similar in that both are weak nitrogenous bases. It was therefore thought possible that nicotine might also be made to combine with peat, and the data here presented show this to be true. The experiments reported, with the single exception noted, were conducted a t atmospheric pressure. I n contrast to the results reported for ammoniated peat, the added nitrogen was completely recoverable as nicotine on distillation with alkali.
Experiments w i t h Florida Sedge Peat
VOL. 28, NO. 5
All the nicotine introduced in the reaction cannot be recovered in the solid product; some remains in the solution. However, the uncombined portion is not wasted but can be regenerated, or the liquid can be otherwise processed for its nicotine in a manner to be described in a future publication. The presence of acids during the reaction is to be avoided, as the nicotine content is thereby lowered. An experiment with acetic acid showed that the peroenta e of nicotine in the product is lowered roughly in proportion to t f e amount of acid present. When nicotine and acid are present in equivalent amounts (as in a salt of nicotine) there is still combination but less than when there is no acid at all.
Preliminary Treatment of Peat with Acid The nicotine content of a nicotine peat can be markedly raised by treating the peat with an acid before submitting it to the nicotine reaction. As has been stated, the acid constituents of peat are combined wholly or in psrt with' bases, such as the alkaline earths, iron, and aluminum, and, to a smaller degree, the alkali metals. With the removal of these bases by an acid, and the consequent liberation of the free peat acids, the nicotine-combining power is increased, especially in the case of the slightly acid, neutral, and alkaline peats which are rich in basic elements. Hydrochloric, nitric, and sulfuric acids are about equally effective in this regard, while acetic acid is somewhat less so.
Nicotine-Combining Power of Various Peats Table I summarizes the results of tests on nine samples of peat. The standard procedure mentioned previously was followed throughout : A mixture of 3 grams of nicotine, 20 grams of peat, and 100 CC. of water was allowed to react on the steam bath for 2 hours. The solid matter was separated by centrifuging, washed on a Buchner funnel, air-dried, ground to 200 mesh, and then analyzed. Where preliminary acid treatment was given, the same quantity of peat was immersed overnight in 3 per cent hydrochloric acid, washed free of excess acid and dissolved salts, and used further without drying in the nicotine reaction. The values for total and for water-soluble nicotine were obtained by the silicotungstate method. The determination of water-soluble nicotine is important, since it affords an index of the water-resisting pro erties of the product. This value should be kept as low as possiile in order that the maximum amount of nicotine shall be retained under wet conditions on the surface to be protected. Water-soluble nicotine is determined at an arbitrary dosage of 5 pounds of nicotine peat to 100 gallons of water, which on a laboratory scale becomes 1gram to 166 cc. The mixture is held at room temperature (25" C.) over a 24hour period
Preliminary experiments on a Florida sedge peat laid the basis for a standard procedure. Combination occurred simply by bringing together nicotine and peat in t,he presence of water. The concentration of nicotine, or of peat, and the volume of water may be varied over a considerable range. I n practice it is desirable to work with a moderate excess of peat in order to utilize fully the more expensive nicotine. A peat-nicotine ratio of 20 to 3 was selected as standard : Twenty grams of peat (air-dried) and 3 grams of nicotine are brought together in the presence of 100 cc. of water. The reaction is conducted at steam-bath temperature (about 100" C.) which results in higher nicoOF NICOTINE PEATS FROM DIFFERENT PEAT SAMPLES TABLE I. ANALYSES tine yields than can be obtained at lower temperatures. A t 200" C., under pressure, the nicotine Degree Acid--Nicotine. of De- ity Air-Dry Basis Organic content falls off appreciably. No experiments were compo- of MoiaOrganic Water- In- Basis made at intermediate temperatures, but there is Peat sition" Peat ture Ash Matter Total sol. sol. T o t d probably no advantage in going above open-steambath temperature. A uniform time of 2 hours is generally allowed for each experiment, although the same results can be achieved in 15 minutes. 3.67 5.52 86.43 3.17 0.81 74 5.9 8.05 Florida sedge The air-dried peat is first ground to about 60 mesh. 8.13 4.84 88.63 7.21 0.95 87 4.1 6.53 Capac Mich., sedge 9.24 82.32 76 5.78 4.76 1.12 5.1 8.44 An interesting but not well-understood factor is the New $ewe, reed 10.14 0.98 82.36 85 7.97 7.50 6.66 4.3 Minnesota reed size of particle as affectin the nicotine content of 10.59 1.63 91.65 9.71 1.19 88 3.8 6.72 German moss the product. Coarse particyes (coarser than 40 mesh) 4.39 3.16 0.65 79 5.3 8.42 19.52 72.06 Manito Ill. reed 5.55 4.30 1.00 77 3.5 7.85 14.68 77.47 seem to produce higher nicotine products than do Cleveland 6hio. reed 2.34 61.14 1.43 0.60 58 6.2 7.87 30.99 London, dhio, reed finer particles (80 mesh or above). This behavior 75 1.28 0.67 0.17 5.6 6.50 40.96 52.55 Stockton, Calif., tule may be due to varying segregation of active and Treated with Hydroohloria Acid inert matter, or to greater removal of nicotine from 9.61 1.01 89 ll56 91.41 8.78 7.03 Florida sedge the finer particles by the wash water, or to still 90.59 9.93 9.00 0.88 90 3.35 6.06 Capac Mich sedge other causes. Since this experiment was performed 13.67 89.63 1.03 92 3.55 12.25 6.82 New jersey r&d 90 11.86 86.24 0.99 7.63 10 23 on only one sample of peat, it should not be con6.13 Minnesota reed 10.85 0.80 92.11 9.99 0.86 91 7.09 German moss cluded that the behavior is ty ical of all peats. 11.77 79.61 9.37 0.89 91 5.48 14.91 Manito I11 reed After the reaction, the soli{ matter is separated 10.01 8.41 0.90 89 6.65 10.30 84.05 Clevelahd 6hio reed 13.16 1.05 88 69.21 9.11 26.27 4.52 by filtration, centrifuging, or settling, and is ultiLondon, dhio! Aed 11.11 6.36 0.92 86 3.60 39.26 57.15 Stockton, Calif.. tule mately washed until the wash water shows only a 4 A, poorly decomposed (closest to living plant)' B, slightly decom osed; C. partly denegligible amount of nicotine (opalescencewith silicocorn osed- D largely decomposed; E, well ddcomposed. Class&ation according to tungstic acid). The product is then air-dried and Dacfnow;ki-Stokes (I). ground to 200 mesh, in which condition it is suitable either for dry-dusting or for use in a spray mixture.
MAY, 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY
and is shaken vigorously at hourly intervals during the working day. The amount of nicotine dissolved is determined as usual in an aliquot of the clear filtrate. Repeated aqueous extraction of the product continues to dissolve out nicotine, but very slowly. At present it is believed that the rate of dissolution is slow enough to afford an adequate period of protection, but this point awaits settlement by special investigation. In addition to total and water-soluble nicotine, analyses were made for moisture and ash, which permit the conversion of total nicotine to a basis of 100 er cent organic matter. Moisture is the loss on drying at 80" (?for 24 hours; ash is the residue after ignition at low red heat. From a practicsl standpoint the airdry basis is the important one, but it is informative also t o compute values to the organic basis, since this permits us t o compare the active matter in the various peats. Determinations of pH were made with the hydrogen electrode on a suspension of peat in water at a ratio of 1 to 5.
Conclusions Several conclusions can be drawn from the foregoing data. I n the first place, the highly acid peats, such as German moss, the Capac, Michigan, and Minnesota peats, are distinctly superior to the less acid types, exemplified by the peats from London, Ohio, and Stockton, Calif. Figure 1 shows graphically the relation between pH and nicotine content on the organic basis. If the Stockton, Calif., and Cleveland, Ohio, peats are disregarded, the various points fall close to the straight line shown. Too much importance should not be attached to this apparent correlation between pH and nicotine content, since acidity in some cases may be due partly to inorganic constituents and hence is not a measure of active organic matter upon which the reaction depends. Secondly, acid treatment in every case raises the nicotine content, and the increase is least for those peats that are naturally very acid and greatest for the more neutral types. The explanation is that, as the basic elements are removed, the acids in the peat are correspondingly freed to combine with nicotine, a process equivalent to base replacement. I n this way a peat-New Jersey reed, for example-which in its natural state possesses a low combining power, can be converted to one ranking among the highest. Of the untreated peats, German moss shows the highest combining power, and acid treatment improves it so little as to make it inferior to other acid-treated peats. Probably also the nature of the peat acids is an important factor. Peat acids of the black, well-decomposed peats (mucks) in general have greater combining power than those of the lighter, less decomposed peats. Thirdly, the nicotine contained in nicotine peat is largely insoluble in water. In the case of untreated peats the in-
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soluble nicotine reaches a value of 88 per cent of the total amount of nicotine present. The nicotine in the acid peats (German moss, the Capac, Michigan, and Minnesota peats) is less soluble than that in the more neutral peats (such as the London, Ohio, and Florida peats). Preliminary acid treatment increases the proportion of insoluble nicotine to over 90 per cent for the better products. This improvement is least for the acid peats, which show a high percentageeven in the untreated state, and marked for the more neutral types. The question of how the nicotine is held in nicotine peat can only be speculated upon a t this time. Clearly it is not a case of free nicotine being adsorbed on the peat, because the product gives a definitely acid reaction which is inconsistent with the presence of a free, strong base. Since nicotine is basic and peat acidic, it is reasonable to infer that a typical acid-base reaction occurs, producing a nicotine salt that is substantially insoluble in water. The practical aim-having the nicotine insoluble-is achieved, irrespective of the explanation. From the commercial standpoint, nicotine peat is a practical product. Peat itself is available in large quantities a t a low price (a few dollars per ton), and the process of manufacture is simple. Nicotine peat, like all nicotine salts, is incompatible with alkaline fungicides. If water-insoluble nicotine insecticides are to be applied with fungicides, the latter should be of a neutral type. Letters patent covering this product and the process of making it have been applied for under the Act of March 3, 1883, as amended.
Acknowledgment Acknowledgment for making the pH determinations with the hydrogen electrode is kindly made to E. H. Bailey, of the Bureau of Chemistry and Soils. M. S. Anderson, of the same bureau, checked the value for the Cleveland, Ohio, peat with the glass electrode.
Literature Cited Dachnowski-Stokes, A. P., U.S. Dept. Agr., Circ. 290 (1933). ( 2 ) Feuatel, I. C., and Byers, H. G., Ibid., Tech. BUZZ.389 (1933). (3) Headlee, T. J., Ginaburg, J. M., and Filmer, R. S., J . Econ. (1)
Entomol., 23, 45 (1930). (4) Scholl, W.,and Davis, R. 0. E., IND.ENG.C H ~ M 25, . , 1074 (1933). (5) Smith, C.R., J . Am. Chem. Soc., 56, 1561 (1934). RECEIVED May 8 , 1935.
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