I N D U S T R I A L A N D ENGINEERING CHEMISTRY
164
Vol. 16, No. 2
Contamination of Beverages and Other Food with Zinc'' By J. W. Sale and C. H.Badger D . C. BUREAUO F CHEMISTRY, WASHINGTON,
HE Navy Department recently transmitted to the Bureau of Chemistry for analysis several bottles of root beer, which the Naval Station a t Guam had reported unfit for human consumption. It was stated that some of the shipment, which consisted of twelve hundred bottles, was sold to a t least twelve people a t Guam, and upon drinking the same they immediately began vomiting. Chemical examination disclosed the presence of zinc in the contents of each of the three bottles examined, and the analysis of a composite sample of 200 cc. from each bottle showed that zinc was present to the extent of 229 mg. per liter, which is equivalent to 3.3 grains of zinc chloride per bottle containing 15 fluid ounces. At about the time the examination of the root beer was completed, four thousand galvanized iron buckets were distributed as premiums in the District of Columbia by a chain of grocery stores. A short time previous a case of mass poisoning by zinc a t a large institution near London had been reported in the literature,2 from which it appeared that over two hundred persons developed typical symptoms of zinc poisoning immediately after a meal consisting of bread, margarine, stewed apples, and tea. Subsequent investigation showed that the apples had been cooked in galvanized iron baskets placed in iron steamers, and that the fruit acids had dissolved the zinc from the baskets. It seems quite probable that some of the buckets being distributed in the District of Columbia and elsewhere would be used for holding semisolid or liquid food, such as cider, lemonade, etc. The matter was considered of sufficient importance for the United States Department of Agriculture to issue a warning against the use of galvanized iron utensils for making preservatives or jellies or as containers for cider or other fruit juices, and to conduct some experiments of a preliminary nature t o ascertain the degree to which ordinary galvanized iron buckets are corroded by some of the commoner liquid foods. The experiments in question were also conducted and the results obtained are reported herein.
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T A B LI-ZINC ~ DISSOLVED FROM GA~VANIZRD IRON PAILS HYDROGEN-ION CONCEN- ACIDITY TRATION EXPRESSSD Cc. 0.1 N ACID PRR LITER After After After 17 41 17 41 Hours Hours Hours Hours 8.4 8.8 0 0 7.5 8.2 1 0 6.4. 6.9 348 96 1109 397 533 493 366
Z I N ~ M GPER . 1,ITRR After After 17 41 At Hours Hours Once Tap watero 5 21 7.2 Distilled water 9 27 6.2 Carbonated water 193 181 5.2 Milk 438 1054 Orangeade 530 854 i:f Lemonade 1411 2700 2.6 a Washington city tap water.
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The galvanized iron pails used in this test were obtained from the supply room of the Bureau of Chemistry. They had been manufactured from 22-gage galvanized sheets. Quantities of 1 gallon each (except milk) of Washington city tap water, distilled water, carbonated water, milk, orangeade, and lemonade were placed in the galvanized iron pails. The quantity of sweet milk used was 1 quart. Samples were examined for zinc a t the end of 17 and 41 hours. The con-
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Presented before the Division of Agricultural and Food Chemistry at the 66th Meeting of the American Chemical Society, Milwaukee, Wis , September 10 to 14, 1923. 2 Lancet, 204, 214 (1923); abstracted in Analysl, 48, 184 (1923). 1
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centration of hydrogen ions and titratable acidity (with phenolphthalein indicator) were also determined on most of the solutions. The orangeade and lemonade contained the juices of twelve oranges and twelve lemons, respectively, and 1 pound of sugar in each gallon. The results obtained are set forth in Table I. Blanks were run on the tap water, distilled water, and carbonated water. The tap water and distilled water contained less than 0.1 mg. of zinc per liter. The carbonated water contained 7 mg. of zinc per liter. This carbonated water had been prepared by mixing cold tap water and carbon dioxide in an ordinary carbonating egg. The amounts of zinc reported in Table I do not include these blanks. No blanks were run on the milk, orangeade, or lemonade. It is probable that the milk contained about 5 mg. of zinc per kilogram before placing it in the galvanized iron pail.3 Rost and Weitze14 point out that the presence of zinc in food is not wholly dependent on the use of galvanized containers, since fresh cows' milk, ordinary drinking water, etc., contain zinc. It will be noted from Table I that the quantity of zinc found after 17 hours increases directly with the concentration of hydrogen ions and with the titratable acidity. The concentration of hydrogen ions and the titratable acidity in general decrease, except in the case of the acidity of orangeade, after 41 hours, with lapse of time due, no doubt, chiefly to the mechanical loss of carbon dioxide in the case of the carbonated water and to the corrosive action of the other liquids on the metal of the container. The acidity of the orangeade after 41 hours had increased from 397 to 533 cc. of 0.1 N acid per liter. This may be explained by the fermentation of the liquid and the formation of carbon dioxide, the experiments being conducted in midsummer. A determination of the volatile and nonvolatile acid of the orangeade after 41 hours showed that the volatile acidity amounted to 244 cc. and the nonvolatile acidity to 289 cc. 0.1 N acid per liter. It is of some interest in this connection t o note that the total acidity of Concord grape juice amounts to about 1330 cc. 0.1 N per liter,b and of apple juice to about 670 cc. 0.1 N per liter.6 The galvanized iron pails which contained the inilk, orangeade, and lemonade were visibly corroded. The visible corrosion was especially marked on the galvanized iron pail which contained the lemonade. The base metal was exposed in one place about the size of a circle having a diameter of 2.5 inches. Aside from the general interest attaching to the apparent solution of a case of food poisoning, these experiments serve to bring freshly to mind the always important question of the metallic contamination of our food. Federal and State inspectors are urged to be always on the lookout for possible metallic contamination, and wherever food is brought in contact with metal to make careful note of the fact so that suitable special investigation can be conducted when such action seems to be advisable. J. Biol. Chem., 38, 191 (1919). Arb. Re+chsgtshamt., 61, 494 (191s); Zenlr. Biochem. BSofihys., 81, 440;C. A . , 14, 1569 (1920). 6 U. S. DePt. Apr., Bull. 666. 8 From unpublished data in Bureau of Chemistry. a Birckner,
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