Method for Debasing
New Jersey Peat L. N. MARKWOOD Bureau of Entomology and Plant Quarantine, U. S. Department of Agriculture, Washington, D. C.
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N COSNECTIOK with the production of the new insecticides nicotine peat and nicotine humate (%') it has been found necessary to remove from peat the inorganic base-forming elements that occur chemically combined as salts of the organic acids present. This removal is accomplished by treatment with acids. The base-forming elements (calcium, iron, aluminum, etc.) are largely removed, leaving the uncombined organic acids. Although complete removal is attained only after repeated extractions with acid, it has been established in the preparation of nicotine peat that a single acid treatment does materially increase the nicotine-combining power of those peats high in inorganic base-forming elements and is therefore sufficient for the purpose in hand ( 2 ) . The process gave no trouble when conducted in the laboratory in numerous trials with various samples of peat. The peat, of about 60-mesh size, was immersed overnight in weak acid, such as 2 per cent hydrochloric acid, and washed on a funnel until free of soluble chlorides. During the research on these insecticides interest centered chiefly on a commercial New Jersey reed peat. This is a dark, well-decomposed product classified as a muck (1). Its p H is 5.1. This specimen, like the various other peats examined, was readily washed free of soluble matter in repeated laboratory tests. The pH of such acid-treated peat is 2.3. A difficulty arose, however, when the process was first tried on a larger scale. For this work a fresh lot of New Jersey peat was purchased. It came from the regular commercial source in 300-pound bags. This product carried a standard moisture content of 65 per cent and felt damp to the touch. A portion of it was immersed overnight in five times its weight of 2 per cent hydrochloric acid. The mixture was strongly acid to litmus. The slurry was transferred to a basket-type centrifuge, which was considered a satisfactory apparatus for industrial washing operations. The expected removal of the liquid and formation of a compact filter cake did not occur. Instead, the basket retained practically all the contents fed to it, both solid and liquid, and because of unequal distribution of the load it soon began to wobble so dangerously that the attempt had to be discontinued. Two questions immediately arose: Why did this lot of peat behave differently from the earlier material? How could the trouble be remedied? The questions were answered partly on theoretical grounds and partly from observation of the difference in physical condition of the two lots. The earlier lot came from a supply that had been stored in the open in burlap sacks for a year or more; it was consequently well dried and had, from the feel of it, probably not more than 10 to 15 per cent of moisture, for it was dry enough to crumble in the fingers. The new lot, on the other hand, was decidedly damp to the touch and by
actual test had the full 65 per cent moisture on which basis it was sold. Of special significance was the spongy, resilient feel, which indicates a cellular or gelatinous condition. This physical difference, arising from the drying out of the raw peat, pointed at once to the method of achieving the desired filtration characteristics. Before an experiment was tried, it was conceived that the damp peat, as purchased, retained in large measure the cellular or gel structure of the original plant material or of its degradation products. The cells were swollen with water and packed down to a practically impervious mat, especially under pressure. Furthermore, diffusion of acid both into and out of the cells was necessarily slow. If the cell walls could be broken or the structure altered the process would be one of flushing rather than diffusion and would consequently be more rapid. A possible explanation, therefore, is that when the peat dried out the cell walls collapsed; perhaps they were ruptured or otherwise altered, with an accompanying breakdown of gel structure, and thus the peat was left in a filterable condition. The first lot of peat had apparently reached this condition by natural drying. Several pounds of the new lot of peat were dried in a chamber over closed steam coils. The material issued very dry and crumbly, and had shrunk considerably. The moisture content was 4 per cent. It was immersed overnight in 2 per cent hydrochloric acid. When the slurry was whirled in the centrifuge, the liquid ran through as speedily as could be desired, and the built-up cake of debased peat was washed free of soluble matter (chloride test) within several minutes. Hence the efficacy of first drying the peat was demonstrated. A total of 500 pounds of New Jersey peat was subsequently processed in several runs in this way, with the use of commercial equipment such as a vacuum dryer or shelf dryer for drying the peat and a centrifuge for washing out the acid and dissolved bases. No difficulty was encountered. Just how far the peat must be dried to permit satisfactory filtration is a matter of opinion. A moisture content of 10 per cent was entirely adequate, whereas 21 per cent was found to be too high; that is, filtration was too slow (distinctly slower than with a 10 per cent product). The information presented here is based upon a study of New Jersey peat. Since different peats vary appreciably in physical properties, it may not be necessary to resort to the drying operation with other types.
Literature Cited (1) Dachnowski-Stokes, A. P.,U. S. Dept. der., Circ. 290, 26 (1933). (2) Markwood, L. N., ISD. ENQ.CHEM.,28, 561, 648 (1936). R E C E I V EJDu n e 13, 1938.
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