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indicated that addition of calcium chloride reduced the necessary amount of lime to a certain point beyond which it was ineffective. If too much was added, the solution appeared to become more acid, and a poor sludge formed. The precipitate which formed was composed mostly of large crystals of calcium carbonate. Microscopic examination of these crystals showed that they had formed in many shapes with large particles of organic or colored matter attached to various faces and corners. Nearly all the crystals examined had a definite brown shade throughout the crystal. Effluent from the first treatment was bleached with chlorine, but such large quantities of chlorine were required that the cost was prohibitive. The chlorides formed tended to increase the dissolved solid matter. An apparent improvement in color was noted before much of the coloring matter had been oxidized. This was due t o the chlorine increasing the acidity of the solution.
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Literature Cited (1) Clark, H. W., Leather Mfr., 41,No. 2 (1930). (2) Eastman, P. A., J . Am. Leather Chem. Assoc., Oct., 1911; U.S. Pub. Health Bull. 100 (Nov., 1919): Hodge, W. W., West Vs. Univ. Coll. Eng., Tech. Bull. 2, 47-61 (1928); Falea, A. L.,IND.ENQ.CH~M., 21, 216 (1929): Tannery Waste Disposal Comm. Penna., J . Am. Leather Chem. Assoc., 26, 70-110 (1931). (3) Eldridge, E.F.,Mich. State Coll. Eng. Expt. Sta., Bull.67,32-47 (1936). (4) Howalt, Wm., and Cavett, E. S., Trans. Am. SOC.Civil Engr., 92, 1351 (1928). (5) Strell, M.,Die SUldtereinigung, 27,257,379 (1935). (0) Wilson, J. A,, “Chemistry of Leather Manufacture”, 2nd ed., New York, Chemical Catalog Co., 1928. PRES~NTBD under t h e title “Colloid Chemistry i n Treatment of Tannery Wastes”, a t t h e Symposium on Colloids and Water and Waste Treatment before the Division of Water, Sewage, a n d Sanitation Chemistry a t the 97th Meeting of the American Chemical Society, Baltimore, Md.
Bromide Residues in Foodstuffs Volatile and Nonvolatile Residues Following Experimental Exposure to Methyl Bromide EDWIN P. LAUG Food and Drug Administration, Washington, D. C.
A microbromide method has been applied to the study of residues of volatile and nonvolatile bromide in foods after fumigation with methyl bromide. Within one hour after exposure, approximately 85 to 95 per cent of the volatile residue disappears from a foodstuff. Under certain extreme conditions, significantly high nonvolatile bromide residues can occur.
might normally be expected-(a) high level of fumigation, (b) long periods of exposure, ( c ) a state of sample subdivision favoring penetration, and (d) lack of adequate ventilation. It was felt that if, under these conditions, methyl bromide still did not leave too excessive residues, there would be little danger to the public health from residues after normal fumigation. To what extent methyl bromide itself may be a residue in fumigated foodstuffs under the conditions of these tests has also been investigated, and a n attempt has been made to determine what correlation, if any, exists between the volatile and nonvolatile residues.
Methods SE of methyl bromide as a fumigant has shown a tre-
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mendous increase within the past several years. One of its chief advantages is its great volatility, a property which should favor its rapid disappearance from foodstuffs during the process of ventilation. Nevertheless, studies on bromide residues in foodstuffs exposed to methyl bromide have shown appreciable increases (8, 4, 6, 6). They are probably caused by certain reactions between methyl bromide and constituents of the foodstuffs which result in the formation of nonvolatile bromide. With the recent unfavorable experience with cyanide fumigation (7) in mind, which resulted presumably from its improper use, this work on methyl bromide was undertaken; the purpose was not to duplicate the experiments cited in the literature having to do with accepted fumigation practices in the trade, but to try to reproduce some of the possible extremes not found in general commercial practice. T o this end four factors were varied in a way designed to produce bromide residues higher than
The micromethod of Dixon ( I ) , as modified by Winnek and was used for the determination of bromine. The proSmith (8), cedure involves dry ashing the sample in the presence of strong alkali, extracting the bromide from the ash with absolute alcohol, oxidizing the bromide to bromate with hypochlorite, and estimating the latter by iodimetry. Witb reasonable care, quantities of bromine of the order of 1 microgram are determinable. Therefore it has become possible to work with 2-gram samples of material instead of the large portions heretofore necessar For determining the volatile bromide, the metho: described by Hahn (3) was used. In principle this is a technique adaptable for the microdetermination of or anic halogens. The organic halide is set free by mild heat an8 aeration, mixed with water, and hydrolyzed to the corresponding acid by passage through a quartz tube maintained at “cherry red” heat. The apparatus is the same as that described and illustrated in Hahn’s paper, and consists of glass and quartz units connected by ground joints. Efficient aeration is secured by suspending the sample, referably as finely divided as possible, in 10 ml. of 50 per cent akohol and maintainin the temperature of this mixture at 70” C . during aeration. b l e s s lar e quantities are present, 20 minutes are sufEcient to remove a i of the methyl bromide. The condensate,
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Vol. 33, No. 6
This fact could be interpreted to mean that the residual methyl bromide present after ex(Samples exposed t o concentrations of 6.9 volume per cent methyl bromide) posure on the gas tends to escape rather than Micrograms Br per Gram (P. P. M.)after: combine further with the sample. Also, the H~~~~ Immediately 1 hour 24 hours 48 hours magnitude of the nonvolatile bromide residue of ExT'olaNon- VolaNon- Vola- Non- Vola- NonAIaterial posure tile volatile tile volatile tile volatile tile volatile bears no clear relation to the volatile. Compare, Ground rat diet 48 2018 636 310 647 57 647 .. for example, the one-hour values in cheese and Am. walnut meats 24 6670 1627 1226 1395 86 1646 , , Am. walnut meats 48 .. 1376 2810 59 28'25 13 2?40 meats' Ital. style grated Table I1 gives the results of analyses for volacheese 24 197 4360 0.0 4090 . . tile and nonvolatile bromide residues 24 and 48 Figs 24 574 19 29 18 15 23 .. .. hours after fumigation. Here again, as in Table I. the relativelv constant values of the nonvolatile residues are in contrast with the progressive which consists of a very dilute solution of hydrobromic acid is decrease in the volatile. Several classes of foodstuffs were collected in 50-ml. Erlenmeyer flasks containing 4 ml. of 0.05 N studied in an effort to determine whether there are any which potassium hydroxide. Quantities as low as 1 microgram of bromight retain excessive amounts of residue. Cheese and nuts, mine can be determined. presumably because of their high fat content, store the largest Since no organic material is present (except traces of acetaldehyde which are driven off when the solution is evaporated to dryamounts, while cereal products and processed dried fruits ness), immediate determination of the bromine can be made follow in the order of decreasing residues. The effect of the without preliminary ashing or extraction. state of subdivision on the penetration of methyl bromide is clearly brought out in the case of the wheat berry and almond. OF BROMIDE RESIDUES IN FOODS TABLE 11. CONCENTRATIONS In every case, less volatile and nonvolatile residues are held 24 and 48 HOURS AFTER 24-HOUR EXPOSURE TO AIR CONTAINING in the intact sample, although in analyzing for the volatile 6.9 VOLUME PERCENTMETHYLBROMIDE constituent, the same factors which prevent the penetration Micrograms of Br per G r a m after: of methyl bromide might also operate here to render the vola24 hours 48 hours Volatile Nonvolatile Volatile Nonvolatile Food tile bromide values less reliable. Particularly with almond, 111 139 34 19 Wheat berry examination of the separate samples analyzed 24 and 48 hours 313 340 75 Ground wheat berry 71 after the experimental fumigation reveals large and erratic 411 408 1.6 3.4 Bleached flour 309 264 1.5 6.5 Wheat germ variations. It must be stressed that, since i t is impossible to 718 716 71 55 Corn meal Trace 60 .. Skim milk powder 1.2 analyze for nonvolatile residue after 24 and 48 hours on the 4090 ... 0.0 Grated Ital. cheesea same sample, it can hardly be expected that the values should 3472 .. 3.3 1.8 Grated Am. cheese 146 17 20 9.0 Whole almond check any closer than they do. 381 372 31 110 Ground almond 2740 2825 13 Am. walnut nieats' 59 I n Table I11 a n additional series of analyses of nonvolatile 23 Pirrn ... ..68 15 bromide is presented. These samples, during and after ex70 6.0 11 XzAcots 10 16 8.0 8.0 Raisins posure to methyl bromide, lay a t the closed end of 24 X 150 64 68 Trace 2.3 Fresh grated cabbage TABLE I. CHABGE IN CONCENTRATIOB OF BROMIDE RESIDUES WITH TIME
..
.t
.Z
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Exposed 48 hours.
Experimental exposure of foodstuffs t o methyl bromide was carried out in a large desiccator of 13-liter capacity. The samples were kxposed in 2-gram portions in 20-ml. aeration tubes. It was found desirable to have the samples as finely divided as possible in order to facilitate not only penetration of the methyl bromide but also its escape during aeration. The source of methyl bromide was a small 10-pound cylinder of the commercial product. The amounts of methyl bromide used for the experimental fumigations were collected and measured over water in a 1000-ml. gas buret. Preparatory to fumigation, the desiccator with samples was slightly evacuated. The required amount of gas from the buret was added, followed by enough air to bring the pressure within the desiccator back to atmospheric. No stirring devices were used, the means for admitting the gas being relied upon to effect reasonably good distribution. The samples rested on a perforated plate about halfway between the bottom and top of the desiccator. Two concentration levels of methyl bromide were used-6.9 and 0.767 volume per cent.
Results Information concerning the volatility of methyl bromide is given in Table I. Calculation shows that after one hour a ground rat diet contains 15.4 per cent, walnut meats 18.4 per cent, and figs 5 per cent of the amount present immediately after the exposure. This amount is further reduced after 24 hours. The plotted points of such data show that the loss of methyl bromide follows a typical degradation curve. Such rapid disappearance from an experimentally treated sample indicates that methyl bromide residues have little or no practical significance. On the other hand, the nonvolatile bromide residue (determined on the same sample after aeration) remains relatively constant and in some cases rather high.
TABLE 111. CONCENTRATION OF NONVOLATILE BROMIDEIN FOODS BEFORE A N D AFTER 24-Hou~EXPOSURE TO AIR CONTAIBIXG 6.9 VOLUME PER CENTMETHYL BROMIDE" Food Wheat berry Ground wheat berry Bleached flour Corn meal Wheat germ Skim milk powder Grated Ital. cheeseb Grated Am. cheese Whole almond Ground almond American walnut meatsb Figs Apricots Raisins Fresh grated cabbage
Micrograms Br/Gram Before exposure After exposure
a After exposure the substance stood 1 week open t o t h e air before sampling. b Exposed 48 hours.
TABLEIV. EFPECTOF CONCENTRATIOX LEVELOF METHYL BROMIDE ON CONCENTRATION OF BROMIDE RESIDUESIX FOODS Food Walnut ground Almond ground Cheese grated Corn meal
Micrograms Br/Gram after 24-Hr. Exposure to: 6.9 vol. 70 CI1aBr 0 8 vol. 7 6 CNaBr Volatile= Iionvolatileb kolatilea Nonvolatileb 59 2770 6 485 110 990 1.5 181 3.3 3251 1.2 815 65 780 14 148
a Values obtained 24 hours after t h e substance had been removed from t h e exposure chamber. b Values obtained 1 week after the substance had been removed from t h e exposure chamber.
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lNDUSTRIAL AND ENGINEERING CHEMISTRY
mm. test tubes in order to restrict somewhat the admission of air currents. I n the case of cheese and nut meats, extremely large bromide residues can occur. Table IV shows the striking differences in concentrations of both volatile and nonvolatile bromide obtained when walnut, almond, cheese, and corn meal are exposed t o the two levels of methyl bromide. The normal schedule for methyl bromide fumigation is 1 t o 2 pounds per 1000 cubic feet. This is in the same range as the lower level used in Table IV (0.767 volume per cent, equivalent to 1.81 pounds per 1000 cubic feet).
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Literature Cited (1) Dixon, W. T., Biochem. J . , 28,48 (1934); 29,86 (1935). (2) Dudley, H.C., IND. ENO.CHEM.,Anal. Ed., 11, 259 (1939). (3) Hahn, F.L.,Milcrochemie, 20,239 (1936). (4) Mackie, D.B.,J . Econ. Entomol., 31, 70 (1938). (5) McLaine, L, S., and Munro, H. A. U., Ontario Dept. Agr. Ann. Rep?., 67, 15 (1936). (6) Stenger, V. A.,Shrader, S. A., and Beshgetoor, A. W., IND. Exo. CHEM.,Anal. Ed., 11, 121 (1939). (7) U. S. Dept. Agr., Food and Drugs Act, Kotice of Judgment 28114 Adulteration of Raisins, 1938. (8) Winnek, P.S., and Smith, A. H., J . Biol. Chem., 119,93 (1937).
Derivatives of Allylic Chlorides J
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Reactions of Methallyl Alcohol' G. HEARNE, M. TAMELE, AND W. CONVERSE Shell Development Company, Emeryville, Calif.
HE preparation of methallyl alcohol by hydrolysis of methallyl chloride was described in the first article (22)of this series. The alcohol is very reactive, as shown by t h e e x t e n t t o w h i c h dimethallyl ether was formed .during the hydrolysis, and it has certain peculiar characteristics, as indicated by the formation of isobutyraldehyde and other products when the hydrolyzate becomes acid. Methallyl alcohol (isobutenol) v a s first synthesized by Sheshukov (91) in 1884, who also studied some of its reactions, but except for Pogorshelski (90)who verified Sheshukov's findings, the alcohol had not been studied prior t o the start of this investigation.
T
methallyl ether is hydrolyzed to methallyl alcohol under the conditions of the rearrangement; so it is possible t o use the entire product from the hydrolysis of methallyl chloride for the production of isobutyraldehyde. A mixture of 90 per cent methallyl alcohol and 10 per cent dimethallyl ether was added a t a rate of 4.1 gallons per hour t o 30 gallons of 12 per cent sulfuric acid in a 37.5gallon autoclave equipped with a stirrer and distillation column. At a kettle temperature of 102" C. and a still head temperature of 61' C., a n azeotrope of isobutyraldehyde and water was removed c o n t i n u o u s l y . From 2780 pounds of the above mixture, 2680 pounds of isobutyraldehyde were obtained, which corresponds t o a yield of 96.4 per cent. The isobutyraldehyde had the following properties: boiling point, 64.1' C.; d*i, 0.795; n'f, 1.3730; boiling point of azeotrope with water (5 per cent water), 60.5" C. Following the reactions of Sheshukov(21) a process has been developed for the production of isobutyric acid from isobutylene. This was placed in semiplant-scale operation at Emeryville at an early date when isobutyric acid was a rather obscure and costly laboratory reagent. The steps in the process and the yield obtainable in each are as follows:
Methallyl alcohol is characterized as a typical reactive allylic alcohol except that it is rearranged to isobutyraldehyde by acids and in some cases by high temperatures. The rearrangement in acid solutions proceeds probably with isobutylene glycol as an intermediate. By varying the conditions, the reaction can be directed to produce isobutylene glycol, isobutyraldehyde, or the isobutylene glycol-isobutyracetal in a good yield. Methallyl alcohol is esterified rapidly by treatment with organic acids in the absence of mineral acids. Met h a or o 1e i n (a m e t h y 1 a cr o l e i n) i Y formed by vapor-phase dehydrogenation or oxidation of the alcohol. The latter is preferred, since it gives a pure product in good yield using silver as a catalyst and steam as a diluent.
Rearrangement and Acetal Formation Sheshukov (91) and later Pogorshelski (20)observed t h a t methallyl alcohol was converted to isobutyraldehyde under the influence of acids. This rearrangement proceeds rapidly when the alcohol is heated with about 12 per cent sulfuric acid, and a n azeotrope of aldehyde and water can be removed continuously by fractionation. If the fractionation is done carefully, isobutyraldehyde is obtained in high purity and almost quantitative yield (16). The process was made continuous by adding methallyl alcohol to the acid solution as rapidly as it was consumed and a t the same time supplying sufficient water t o maintain the acid concentration. Di1
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The first two papers in this series appeared in January and March, 1941.
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1. Chlorination of isobutylene t o methallyl chloride; yield 85-90 per cent (1). 2. Hydrolysis of methallyl chloride to methallyl alcohol and dimethallyl ether; yield, 90-95 per cent (88).
