August, 1945
ANALYTICAL EDITION
3. 0.1 ml. of a mixture of 1 volume of concentrated hydrochloric acid, 9 volumes of saturated chlorine water (0.6 gram per 100 ml.), and 90 volumes of water. 4. 0.05 ml. of 0.6% hydrogen peroxide solutibn, followed b y 0.05 ml. of concentrated hydrochloric acid. 5 . 0.05 ml. of a mixture of 9 volumes of concentrated nitric acid and 1 volume of concentrated hydrochloric acid. Any of these mixtures will give a color with caffeine in dilutions u p t o 1-20,OOO. All b u t No. 4 will give tests u p to 1-40,000, and No. 2 will give a trace of color with a 1-80,000 dilution of caffeine. T h e presence of hydrochloric a i i d appears to be essential for maximum sensitivity, whatever the oxidant used. During t h e evaporation and subsequent heating exposure to steam should be avoided, as i t was found t o cause wide variations in results. Use of a h o t plate, operating at or below steam bath temperature, IS recommended. I n producing t h e final color all the compounds tested, including water h u t excepting aniline a n d dimethylaniline, changed the colors of the residues t o a uniform purplish red, varying in persistence b u t of equal intensity, except for ammonia vapor which gave a more intense b u t relatively fugitive color. Triethanolamine is recommended since it gives a solution whose color fades very slowly, persisting for several weeks, which makes i t suitable for use in quantitative applications of the test. A mixture of equal volumes of triethanolamine and water is satisfactory. During t h e course of the work evidence was obtained t h a t losses of caffeine, significant when working with minute amounts m a y occur during evaporation of its aqueous solutions and by sublimation. For this reason heating of dry residues suspected of containing the drug should not be prolonged, and solutions should not be evaporated before adding the oxidizing mixture.
SUMMARY
-4 color test for caffeine has been investigated and standardized t o produce sensitive and reproducible results when minute amounts of the drug are present. T h e test is conducted by adding a specified amount of any one of five oxidizing mixtures t o 0.1 ml. of a caffeine solution, evaporating to dryness, preferably on a low-temperature hot plate to avoid contact with steam, continuing heating until maximum color is developed, and finally adding 0.05 ml. of a triethanolamine solution. T h e test can be made quantitative b y the use of caffeine standards because of t h e persistence of the final color produced.
LITERATURE REVIEWED
(1) “Allen’s Commercial Organic Analysis”, 5th ed., Vol. VII, Philadelphia, P. Blakiston’s Son & Co., 1929.
Autenrieth, Wilhelm, tr. by Warren, W. H., “Laboratory Manual for Detection of Poisons and Powerful Drugs”, 6th ed., Philadelphia, P. Blakiston’s Son & Co., 1928. Brunn, O.,Ber., 21, 513 (1888). Ekkert, L., Pharm. Zentralhalle, 72, 481 (1931). E’ne, G. E., and Vanderkleed, C. E., J . A m . Pharm. Assoc., 3, 1681 (1914). Fuller, H. C., “Chemistry and Analysis of Drugs and Medicines”, New York, John Wiley & Sons, 1920. Giovanni, Issoglio, Industria chimica, 4, 458-61 (1929). Maly, R., and Andreasch, R., Monatsh.. 3, 92 (1882). Maly, R., and Hinteregger, F., Ibid., 3, 85 (1882). Miko, J. V., and Miko, S. V., Pharm. Zentralhalle, 67, 193 (1926).
Nestler. A . , 2. L’ntersuch. Nahr. Genussm., 4, 289 (1901). Rochleder, F., Ann., 63, 193 (1847); 69, 120 (1849): 71, 1 (1849).
Rosenthaler, L., “Toxikologische Mikroanalyse”. Berlin, Gebriider Borntraeger, 1935. Schaer, E., Apoth. Ztg., 25, 705 (1910). Schwarzenbach, Z . anal. Chem., 1, 229 (L862). Stenhouse, J., Ann., 45, 366 (1843). Tunmann, O., Chem. Zefitr. 11, 42 (1919). Wende, E.. Apoth. Ztg., 34, 95-6 (1919).
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BOOK REVIEW The Analysis of Foods. Andrew L. Winton and Kate Barber Winton. 999 pages, 208 illustrations. John Wiley and Sons, Inc., New York; Chapman and Hall, Ltd., London, 1945. Price, $12.
The names of Andrew L. and Kate Barber Winton are writ large in the literature relating to the chemistry and histology of foods. The excellent teamwork which they displayed in their compendious four-volume treatise on “The Structure and Composition of Foods” is again exemplified in the present work. A companion volume dealing with the analytical methods by which the composition of foods is determined was in fact an almost inevitable consequence of their previous publication and, in accomplishing this result, the authors, drawing upon the results of their long practical experience in federal, state, and private laboratories and upon the observations of foreign study and travel, have prepared a work of inestimable value to all food chemists, whether engaged in agricultural, industrial, nutritional, and regulatory investigations, or occupied in the associated fields of biological and physiological research. Breaking loose from the restrictions imposed upon him by the long re-editing of A. E. Leach’s “Food Inspection and Analysis”, Dr. Winton in the present work found himself free to adopt an entirely new presentation of his own which is outlined on the inside of the front cover. The subject matter is divided into two main divisions: Part I (416 pages) describes the general analytical methods (microscopic, physical, and chemical) for determining (1) elementary and (2) proximate constituents of foods, including (3) water, (4) protein, (5) fat, (6) nifext (a code word for the cumbersome term nitrogen-free eztract), (7) fiber, (8) ash (including major and minor mineral elements), (9) alcohols, (10) vitamins, (11) natural and (12) artificial colors, and (13) chemical preservatives. Part I1 (530 pages) describes the special analytical methods for each of the 12 classes of food products: A cereals, B fats, C vegetables, D fruits, E sugars, F alcoholics, G dairy products, H animal foods, I alkaloidal products, J food flavors, K leaven, L salt. Running heads on each page, indicating class, group, and subdivision, assist making cross references within the book. Full bibliographic references a t the end of each section indicate original sources of information. Economy of space is achieved by a double-column arrangement of the text. While every food analyst has his own preferences as regards general and special schemes of analysis, the selections described by the Wintons represent a wide liberal choice of the best available methods; among them are many that have been tested and approved by the Association of O5cial Agricultural Chemists, in the affairs of which Dr. Winton, as a former president and executive, took a prominent part for many years. As for their choice of methods the authors remark in the preface: The analysis of methods has demanded quite as much attention some cases almost hopeless-task of the compilers has been the separation of the method proper from its entanglement with experimental and dlscussion in journal articles and the piecing together of the parts to form a lucid and usable whole . . . . . . A method is considered to be amprocedure in which a basic reaction, a special reagent, or a physical operation is used for the first time for the particular purpose and a modification as a method that has been distinctly improved in accuracy or convenience without a change in the fundamental features . . . . . . . In the triple designation of a method, first the originator is given, second the distinctive reagent, or reaction product, and third the class to which the method belongs. as the analysis of foods. In fact, the most di5cult-in
The scrupulous care of the authors to give full credit to the originators of methods is especially to be commended at a time when attention to such matters of etiquette is all too often neglected. The book is provided with an excellent 52-page index. The cuts of apparatus, graphs, and microscopic sections are well executed. Only a few typographical slips were noted, such as a misplaced decimal point, or a wrong algebraic sign-errors such as inevitably creep into a complex formula or escape the tired eye in the reading of proof. Dr. and Mrs. Winton are to be congratulated upon adding so worthy a volume to their list of publications on the chemistry, composition, and microscopy of foods. i.A. BROWSE
