levulose in 20-ml portions by the Jackson-Mathews procedure, p. 203, estimating copper by any desired method except that of direct weighing of the copper precipitate. Titrate the remainder of the solution against 10 ml of Soxhlet solution. If the titer is less than 15 ml, dilute 100 ml to 250 ml and repeat the titration. Determine the sucrose by the invertase Clerget analysis. The calculation of results, made by successive approximation, is illustrated by an example. A sample, 64.60 g containing 62.5 g of sucrose, gave a Lane and Eynon titer of 18.13 ml which, estimated as invert sugar, indicated 239.4 mg of reducing sugars per 100 ml. By the Jackson-Mathews method, 76.9 mg of reduced copper was found; from which 9.0 mg is deducted to correct for the reducing action of 5 g of sucrose. By table 93, p. 597, 67.9 mg corresponds to 22.0 mg of apparent levulose in 20 ml of solution, or 110.0 mg in 100 ml. Total reducing sugars as invert.. Apparent dextrose, first approximation, 239.4-110.0. Apparent levulose, second approximation, 110.0-10.4 Apparent levulose, third approximation, 110.0-11.3.. Mg 239. 4 110. 0 129. 4 10. 4 99.6 139.8 11. 3 98.7 140. 7 The levulose equivalent of the dextrose, 140.7÷12.4, is again 11.3, so that further approximation is unnecessary. The ratio of levulose to dextrose is thus found to be 98.7 to 140.7, or 41 to 59. From table 90, p. 596, the factor is 43.3, and total reducing sugar, 238.8 in 100 ml. Calculated for original sample, levulose is 0.382 percent; dextrose, 0.542 percent; and total reducing sugar, 0.924 percent. In a further study of raw-sugar analysis, Zerban [21] has compared the Browne method of polarizing constants with the method of total reducing sugar combined with selective methods for sucrose and levulose. He devised a less laborious method of calculation than that of successive approximations. Thus in which x and y are the milligrams of dextrose and levulose, respectively, in 100 ml of solution analyzed; R is milligrams of total sugars, expressed as levulose by Lane and Eynon titration; and R1, the milligrams of apparent levulose determined by the Jackson-Mathews method and corrected for the reducing effect of the sucrose. The factor, 0.0806, is the constant reducing ratio of dextrose to levulose, 12.4 mg of dextrose having the same reducing effect as 1 mg of levulose. Solution of eq 57 and 58 gives x=mg of dextrose in 100 ml of solution R-R1 y=mg of levulose in 100 ml of solution=R—ar. The calculation is facilitated by the factors in table 91, p. 596, which is abbreviated from the expanded form given in the reference cited. Interpolation yields the true factors accurately. The simplified method of calculation is not as rigorous as the method of successive approximations, but the errors for small percentages of total sugars are within the error of experiment. For samples containing large amounts of reducing sugar in the presence of small amounts of sucrose, the successive approximation method is to be recommended. The analytical procedure is described on page 227. Some typical analyses of individual samples are shown in table 30, p. 227. In table 30 are also given the averages of a large number of samples of different geographical origin. Interesting analyses were made of two pairs of samples produced from the same Cuban plantation in the crop year 1934. The A samples were manufactured in 1934, the B samples in 1935. In both cases the amount of total reducing sugars in the old-crop samples is more than twice that in the new crop, and at the same time the dextrose is very much higher. There is strong indication that the old-crop sugars have undergone inversion during storage and that levulose has been destroyed through the activity of torulas. (2) SUCROSE, DEXTROSE, AND LEVULOSE IN CANE MOLASSES.Erb and Zerban [22] extended the work of the New York Sugar Trade Laboratory to the determination of total reducing sugars, dextrose and levulose, in cane molasses. Total reducing sugars were determined by the Munson and Walker method in samples containing 0.4 g of total sugar. In amplification of the tables of Munson and Walker, they determined the copper value of sucrose mixed with pure dextrose and pure levulose, respectively, and also revised the tabulated values of sucrose-invert-sugar mixtures, deriving the formulas D=0.38476 CuO+0.00009436 CuO2-3.177, L=0.4305 CuO+0.0000611 CuO-3.412, I=0.40016 CuO+0.00009631 CuO2-2.9911, which are valid for 0.4 g of total sugar. The revised values for invert sugar show, for concentrations of sugar above 150 mg., slightly higher weights of sugar than those of Munson and Walker for the same weights of copper. For the analysis of molasses, total sugars were determined by the Munson and Walker method, as described above, and levulose was determined selectively in the same filtrate by the Jackson-Mathews procedure, page 203. The experimental data were solved for the respective figures by substitution in the formulas the sucrose having been determined previously by the Clerget method. R1, total reducing sugars, expressed as levulose (table 92, p. 597), and R2, the apparent levulose (table 93, p. 597), after deducting from the total copper precipitated the weight of copper reduced by the sucrose, p. 227. These formulas are similar to those derived for the raw-sugar analysis, but the a's now have different values because of the difference in method of total reducing-sugar analysis. The solution of these equations is greatly facilitated by use of the expanded table published by the authors. Here it is possible to include the table only in greatly abbreviated form, but interpolation yields correct figures for intermediate values of CuO. (d) ANALYSIS OF A MIXTURE OF THREE SUGARS BY THREE REDUCTION PROCESSES (1) STEINHOFF METHOD FOR DEXTROSE, MALTOSE, AND DEXTRIN [23]. Steinhoff has based a proposed method for the simultaneous determination of the three carbohydrates upon the assumption that all dextrins in starch-conversion products are nonreducing toward Fehling solution. In outline, he determined dextrose selectively by a modification of the Barfoed method, total reducing sugar by Fehling solution and total dextrose produced by complete hydrolysis of the mixture. The required reagents consist of Soxhlet solutions I and II (p. 170), and III, a 50-percent sodium-acetate solution. Prepare also 0.1 N iodine and 0.1 N thiosulfate. Weigh 8.75 g of commercial glucose sirup and make to 500 ml. (Solution a). For complete hydrolysis, transfer 50 ml to a 100-ml volumetric flask, add 25 ml of 3 N hydrochloric acid, and digest for 22 hours in a boiling-water bath. Cool, neutralize with sodium hydroxide, and fill to mark. (Solution b). Reducing-sugar analysis is carried out in three 200-ml Erlenmeyer flasks. Analysis A.-For selective dextrose analysis take 10 ml of Soxhlet solution I, 20 ml of solution III (sodium acetate), 10 ml of water, and 10 ml of solution a. Analysis B.-For total dextrose and maltose, take 10 ml each of Soxhlet solutions I and H, 20 ml of water, and 10 ml of solution a. Analysis C.-For total sugar in the hydrolyzed solution take 10 ml each of Soxhlet solutions I and II, 20 ml of water, and 10 ml of solution b. This aliquot sample contains half as much of the original sample as analyses A and B. Hence the dextrose observed is multiplied by 2 to correspond with that derived from a 175-mg aliquot. All three flasks are brought to boiling and ebullition is continued for 2 minutes, or preferably allowed to stand in a boiling water bath for 20 minutes. Dissolve the cuprous oxide precipitate in hydrochloric acid, neutralizing the excess acid with sodium bicarbonate. Measure in an excess of 0.1 N iodine, and after cooling the solution, titrate the excess of iodine with thiosulfate. Calculate the number of milliliters of 0.1 N iodine consumed. in which D is the weight of dextrose found by analysis A when referred to column 1 of table 104, p. 609; M is the weight of maltose which corresponds to the milliliters of 0.1 N iodine which is obtained if the volume used in analysis A but calculated to Fehling solution by column 2 is deducted from the volume of iodine consumed in analysis B. Tis the weight of total dextrose corresponding to the volume of iodine consumed in analysis C; and W is the weight in milligrams in the respective aliquot samples, that is, 175 mg. Example.-8.75 g of a glucose sirup was analyzed as described above. Analysis A.-9.17 ml of 0.1 N iodine was consumed. The aliquot contained 175 mg of the original sample. The 9.17 ml corresponds to 26.25 mg of dextrose. Analysis B.-16.60 ml of iodine was consumed. According to the table, 9.17 ml of iodine (analysis A) is equivalent to 8.24 ml when the analysis is carried out by the Soxhlet reagents. Hence, by deducting the reduction by dextrose, 16.608.24 8.36, we obtain the reduction caused by maltose. This volume of iodine corresponds to 45.5 mg of maltose by column 3 Analysis C.-21.56 ml of iodine was consumed by a sample half as great as in the preceding analysis. This corresponds, by column 4, to 72.82 mg of dextrose, which, multiplied by 2, equals 145.64 mg from a 175-mg sample. Deduct the dextrose and maltose already present before hydrolysis, that is, 26.25+45.5= 71.75. [1] R. F. Jackson, J. Assn. Official Agr. Chem. 13, 198 (1930). [2] C. A. Browne, J. Am. Chem. Soc. 28, 439 (1906). [3] C. A. Browne, Handbook of Sugar Analysis, (John Wiley & Sons, New York, N. Y., 1912). [4] O. Gubbe, Ber. deut. chem. Ges. 18, 2207 (1885). [5] Wiley Agricultural Analysis 3, 267 (1897). [6] R. F. Jackson and J. A. Mathews, J. Research NBS 8, 419 (1932) RP426. [7] R. E. Lothrop, J. Assn. Official Agr. Chem. 21, 419 (1938). [8] A. W. van der Haar, Biochem. Z. 81, 263 (1917). Chem. Weekbl. 13, 1204 (1916). cf. Anleitung zum Nachweis, zur Trennung und Bestimmung der Monosaccharide und Aldehydsäuren (Gebrüder Borntraeger, Berlin, 1920.) [9] S. F. Acree, Chem. Abst. 15, 2545 (1921). [10] E. Bourquelot and H. Hérissey, Compt. rend. 129, 339 (1899). [11] H. Pellet, Bul. assn. chim. sucr. dist. 16, 1181 (1898–99); 18, 758 (1900–1901). [12] C. Neuberg and J. Wohlgemuth, Z. physiol. Chem. 35, 31 (1902). cf. C. Neuberg, Ber. deut. chem. Ges. 35, 2243 (1902). [13] A. D. Dickson, H. Otterson, and K. P. Link, J. Am. Chem. Soc. 52, 775 (1930). [14] D. R. Nanji, F. T. Paton, and A. R. Ling, J. Soc. Chem. Ind. 44, 253T (1925). [15] C. A. Browne and M. Phillips, Int. Sugar J. 41, 430 (1939). [16] R. L. Whistler, A. R. Martin, and M. Harris, J. Research NBS 24, 13 (1940) RP1268. [17] K. V. Lefèvre and B. Tollens, Ber. deut. chem. Ges. 40, 4513 (1907). [18] W. F. Hillebrand and G. E. F. Lundell, Applied Inorganic Analysis, p. 623 (John Wiley & Sons. New York, N. Y., 1929). [19] W. B. White, Bul. 234, New York State Dept. of Agr. and Markets (1930). [20] F. W. Zerban and M. A. Wiley, Ind. Eng. Chem., Anal. Ed. 6, 354 (1934). [21] F. W. Zerban, Ind. Eng. Chem., Anal. Ed. 8, 321 (1936). [22] C. Erb and F. W. Zerban, Ind. Eng. Chem., Anal. Ed. 10, 246 (1938). [23] G. Steinhoff, Z. Spiritusind. 56, 64 (1933). XI. ANALYSIS OF SPECIAL PRODUCTS 1. HONEY [14] (a) PREPARATION OF SAMPLE (1) LIQUID OR STRAINED HONEY.-If the sample is free from granulation, mix it thoroughly by stirring or shaking before weighing portions for the analytical determination. If the honey is granulated, place the container, having the stopper loose, in a water bath and heat at a temperature not exceeding 50° C, with occasional stirring until the sugar crystals dissolve. Mix thoroughly, cool, and weigh portions for the analytical determinations. If foreign matter, such as wax, sticks, bees, particles of comb, etc., is present, heat the sample to 40° C in a water bath and strain through cheesecloth in a hotwater funnel before weighing portions for analysis. (2) COMB HONEY.-Cut across the top of the comb, if sealed, and separate completely from the comb by straining through a 40-mesh sieve. When portions of the comb or wax pass through the sieve, heat the sample as in (1) and strain through cloth. If the honey is granulated in the comb, heat until the wax is liquefied; stir, cool, and remove the wax. (b) MOISTURE Proceed as directed under (c), page 262 of this circular. (c) ASH Weigh 5 to 10 g of honey into a platinum dish, add a few drops of pure olive oil to prevent spattering, heat carefully until swelling ceases, and ignite at a temperature not above dull redness until a white ash is obtained. (d) DIRECT POLARIZATION-TENTATIVE (1) IMMEDIATE DIRECT POLARIZATION.-Transfer 26 g of the honey to a 100-ml flask with water, add 5 ml of alumina cream, dilute to the mark with water at 20° C, filter, and polarize immediately in a 200-mm tube. (2) CONSTANT DIRECT POLARIZATION.-Complete the mutarotation by allowing the solution prepared for polarization to stand overnight before making the reading or by adding a few drops of NH,OH to the solution before making to volume. If necessary to conserve the sample, the solution from the tube used in the immediate direct polarization (1) may be returned to the flask. Make the final reading at 20° C in a 200-mm tube. (3) MUTAROTATION.-The difference between (1) and (2) is a measure of the mutarotation. (4) DIRECT POLARIZATION AT 87° C.-Polarize the solution obtained under (2) at 87° C in a jacketed 200-mm metal tube, preferably of silver. (e) INVERT POLARIZATION-TENTATIVE (1) AT 20° C.-Invert 50 ml of the solution obtained under (d), using either invertase or hydrochloric acid as directed on pages 157-58, or page 155 this Circular, and polarize at 20° C in a 200-mm tube. (2) AT 87° C.-Polarize the solution obtained under (1) at 87° C in a 200-mm tube. |