The distillation should be conducted at such a rate that 100 cc of the distillate may be obtained in from twenty-five to thirty-five minutes. Occasionally some paraffin is carried over mechanically, and this may usually be removed from the surface of the distillate by means of a wire or glass rod. The following results were obtained on ketchups containing a known amount of sodium benzoate: Determination of sodium benzoate in ketchup by Method V (West). The statement has frequently been made that cinnamic acid is being used for the preservation of foods, especially in the case of tomato ketchup. The claim has often been made by those interested in the preservation of ketchup with benzoic acid that the presence of cinnamic acid could not be detected and that firms claiming to use no preservative were preserving with that substance. Two qualitative methods for the detection of cinnamic acid, differing slightly from each other, were elaborated by P. B. Dunbar. Both of these methods depend upon the well-known fact that cinnamic acid is oxidized to benzaldehyde by dilute chromic acid mixture. Method 1.-One hundred grams of ketchup were treated with 100 cc of water and 5 cc of sulphuric acid (1 to 5) and the mixture extracted directly with three portions of chloroform, using 50, 25, and 25 cc, respectively. The chloroform extract was made alkaline with ammonia and evaporated to dryness on the water bath. The residue was dissolved in a small amount of hot water, filtered, again evaporated to dryness, and heated to boiling with 5 cc of dilute chromic acid mixture (1 part of dilute sulphuric acid saturated with potassium bichromate and 7 parts water). The odor of benzaldehyde is strongest when the mixture is cooled until the fumes of sulphuric acid are no longer apparent. Method 2.-Two hundred grams of the ketchup are diluted to 500 cc with water, allowed to settle, and filtered. An aliquot portion of the filtrate, 250 cc or more, is acidified with 5 cc of sulphuric acid (1 to 5), extracted with chloroform, and the remainder of the operation conducted as under Method 1. The second method appears to be slightly more delicate than the first, although with either it was possible to detect cinnamic acid in tomato ketchup when present to an extent of 25 mg per kilogram. This reaction is also given by cinnamic aldehyde. The method, therefore, does not distinguish of itself between cinnamic aldehyde, resulting from the use of cinnamon as a flavor and cinnamic acid used as a preservative, except that the amount of cinnamic aldehyde present in the commercial ketchups examined was not sufficient to give a reaction. If cinnamic acid were present in the ketchup, it would be detected by the methods used for the detection of benzoic acid. Cinnamic aldehyde, on the other hand, would not be detected by the methods suggested for benzoic acid. The benzoic-acid residue obtained by the evaporation of the chloroform extract may be examined by the cinnamic-acid methods described. The germicidal and antiseptic properties of cinnamic acid were investigated by G. W. Stiles, who found them to be very much lower than those of benzoic acid. The preservation of a food, therefore, would require a much larger percentage of cinnamic acid than benzoic acid. In fact, the antiseptic properties of a saturated solution of cinnamic acid are so slight that this substance would probably not serve as a preservative for foods. A method for the separation of benzoic acid and cinnamic acid by precipitation of the latter with manganous salts a was tried unsuccessfully by Mr. Dunbar, who was unable to secure a precipitation of either benzoate or cinnamate of manganese in dilute solution. As is to be expected, Mohler's and Peter's reaction also give the same end reaction in the presence of cinnamic acid. REPORT ON TEA, COFFEE, AND COCOA. By A. G. WOODMAN, Associate Referee. The work of the referee for the past year has been limited to a study of methods for the determination of caffein and caffetannic acid in coffee, extract in tea, crude fiber and starch in chocolate, and sugars in milk chocolate. Twenty-two samples were prepared and sent out to those who had expressed a willingness to collaborate, ten on tea and coffee and twelve on cocoa products. These were accompanied by the following directions and a letter of transmittal: CAFFETANNIC ACID. (a) Krug's method.-Proceed as directed in Bul. 107, p. 155. _ (Note that the formula for lead caffetannate should be Pb(CHO), as in Bul. 107, Rev.) Save the filtrate for the determination of caffein. After weighing the lead caffetannate determine its lead content as follows: Digest with aqua regia, add sulphuric acid, heat to fumes, cool, dilute, add alcohol, settle, filter, ignite, and weigh as lead sulphate. Calculate as per cent of lead. (b) Method of Trillich and Göckel.b-Boil 3 grams of coffee one-half hour with water, filter, and repeat this treatment on the residue three times. The united filtrates are made up to 1,000 cc. To 400 cc add 1 cc of basic lead acetate solution and allow to stand overnight. Filter, wash, decompose the precipitate with sulphuretted hydrogen, filter from lead sulphid, evaporate to dryness, and weigh. CAFFEIN. In the filtrate from the lead caffetannate precipitate the lead with hydrogen sulphid, filter, and remove the excess of hydrogen sulphid by boiling, concentrating the solution, if necessary, to about 100 to 150 cc. Add tenth-normal potassium iodid solution of iodin in excess, filter through a little glass wool and determine the excess of iodin with tenth-normal sodium thiosulphate. 1 cc tenth-normal iodin equals 0.00485 gram caffein.c EXTRACT IN TEA. (a) Follow the provisional method as described in Bul. 107, p. 149. (b) Follow the method proposed by Doolittle and Woodruff (Bul. 105, p. 48). CRUDE FIBER (SAMPLE A). Proceed as directed in Bul. 107 under “VI. General Methods," 11, page 56, except that the fiber is filtered and weighed on a paper. The sample should be pulverized by grinding with ether as described in the succeeding paragraph. CRUDE STARCH (COPPER-REDUCING MATTERS BY DIRECT ACID HYDROLYSIS), SAMPLE A. Weigh 4 grams of the material if unsweetened, or 10 grams if sweetened, into a small wedgewood mortar, add 25 cc of ether and grind with a pestle. After the coarser material has settled decant off the ether together with the fine suspended matter on a Scoville, Amer. J. Pharm., 1907, 79 [12]: 549–551. bZts. Nahr. Genussm., 1898, 101. Gomberg: J. Amer. Chem. Soc., 1896, 18: 331. Conduct a 11 cm, blue ribbon, S. and S. paper. Repeat this treatment until no more coarse material remains. After the ether has evaporated from the filter, transfer the fat-free residue to the mortar by means of a jet of cold water and rub to an even paste, filtering on the paper previously employed. Repeat this process until all sugar is removed. In the case of sweetened products the filtrate should measure at least 500 cc. the hydrolysis of the residue as directed for "Starch" under "VI. General Methods," 8 (a), page 53, Bul. 107, Rev., except that after neutralizing with sodium hydroxid, add 5 cc of basic lead acetate solution (prepared as directed under "VI. General Methods," 6 (b), (1), page 40) before completing the volume to 250 cc. To 100 cc of the filtrate add 1 cc of 60 per cent sulphuric acid, filter off the lead sulphate and determine reducing matters in 25 cc of the filtrate as directed under "VI. General Methods," for Reducing Sugars, 7, (b), (2), page 49. Determine copper by the direct weighing of cuprous oxid, 7, (c), (6), page 53. SUGARS (SAMPLE B). Determine the lactose and sucrose as described by Dubois.a The amount of work requested was purposely made small in order that it should not prove burdensome, but in spite of this results were received from only four chemists, two on cocoa products and two on tea and coffee. TEA AND COFFEE. The results on tea and coffee are shown in the following table: Krug method for caffetannic acid.—(1) The water must be kept to constant volume during thirty-six hours' digestion. (2) Unless great care is used, the addition of lead acetate to the hot alcohol solution will cause violent ebullition and partial loss of contents. A safety tube helps to overcome this difficulty. (3) In determining the lead content of the caffetannate it is advisable to filter the caffetannate through a tared gooch. This will allow of digestion of contents in nitric acid and precipitation of the lead with sulphuric acid without using a filter paper, the carbon of which does not completely oxidize and produces a blackening of the lead sulphate. The final weighing of the sulphate should also be made in a gooch. a J. Amer. Chem. Soc., 1907, 29: 560. Caffein method.—It is suggested that the caffein iodin precipitate does not form immediately and that the low results are due to filtering and titrating the solution too quickly. Other work indicates that after the iodin is added the flask should be allowed to stand in an ice chest overnight before titrating. Much better results can be secured by Gomberg's original method for caffein, as given in the Journal of the American Chemical Society (1896, 18: 331), and modified as follows: Extract 2 grams some time with four portions of water, cool, and make to 1,000 cc. Treat 500 cc with 15 cc of saturated lead acetate solution, let settle, filter, remove lead with hydrogen sulphid, boil off excess of hydrogen sulphid, divide filtrate into two parts, concentrate each to 50 cc, add 0.2 cc of concentrated hydrochloric acid to one and 0.5 cc of acetic acid to the other, cool to 15° C., add 20 cc of tenth-normal iodid solution, stopper flask, and let stand in ice two hours, filter on a gooch. Caffein does not precipitate unless mineral acid is present, so the acetic acid portion shows if any other materials are present which would precipitate with the iodin solution. If any absorption of iodin is found in the acetic portion, it must be deducted from the titration containing mineral acid. The difference represents the iodin used up in the formation of the periodid of caffein: 1 cc of tenth-normal iodin equals 0.00485 gram of caffein. Using this method, 0.78 per cent of caffein was obtained from the coffee reported. Krauch method for extract in tea. The bulk of sample (20 grams) makes complete removal of water-soluble substances almost impossible. The absorption of water by large filter paper and on surface of flask during weighing is also a serious objection to the method. If sample is ground, filter paper is clogged and filtration prevented. Doolittle and Woodruff method.-Care should be used to keep the entire sample in the boiling liquid during extraction or low results will be obtained. Any loss of water by evaporation should be replaced. NOTES BY REFEREE. The discrepancy in the results obtained by the two analysts with the Trillich and Göckel method is due principally to the fact that Mr. Woodruff used 5 cc of basic lead acetate in the precipitation instead of 1 cc, as prescribed in the method. Determinations made by the referee on the same sample gave 10.08 per cent where 2 cc of basic lead acetate was used and 12.04 per cent when 4 cc was used. The lower results obtained by Mr. Woodruff in the caffein estimation may have been due to the greater volume of solution in which the caffein periodid was precipitated, he using a volume of 100 to 150 cc, while the referee employed a volume of 20 cc. Experiments made by Mr. W. C. Taylor in the writer's laboratory have shown the necessity for concentrating the caffein solution to small bulk. The determinations made of extract in tea by the referee convinced him of the great superiority of the Doolittle and Woodruff modification over the Krauch method as regards convenience, time, and liability to error. COCOA PRODUCTS. The following results were obtained from the collaborating chemists on cocoa products: COMMENTS BY ANALYSTS. G. M. Bartlett: The conversion of the starch was carried out as outlined, no difficulty occurring in the procedure. The aliquot for precipitation was obtained as follows: After converting, neutralizing, and adding basic lead acetate the sample was made up to volume at about 35° C. To 100 cc at this temperature was added the 60 per cent of sulphuric acid, cooled so that the volume of liquid contracted to 100 cc. It was necessary to cool only to about 18° C. The sample for precipitation was taken when the liquid had contracted to the mark. Two determinations were made-one by precipitating by the Walker-Munson method (J. Amer. Chem. Soc., June, 1906,) and the other following the method in Bulletin 107. The latter gave 11.83 per cent of starch. In determining crude fiber the electric stove was used for boiling the 1.25 per cent sulphuric acid and caustic soda. There was but little frothing. The filter paper and crude fiber were dried at 100° C and over sulphuric acid. During weighing the filter paper gained in weight. I do not care for this method of getting the weight of the crude fiber, even though it is not to be ignited, and would prefer filtering on a weighed platinum gooch filter. In calculating the sugar in chocolate by Dubois's method a it seems illogical to multiply (a-b) by 1.05x (x equaling the volume obtained by dissolving sugar in 100 cc of water) rather than by 105 plus the increase in volume due to the solution of the sugar. This actually makes but little difference in the result, but the following statement of the formula seems preferable: Where increase of volume owing to the solution of the sugar in water. In calculating the lactose the complete formula reads: Per cent lactose=CX4×1.11×1.05x X1.264, where x=volume of solution when the sugar is dissolved in 100 cc. R. W. Hilts: The samples on arrival were immediately placed in glass-stoppered bottles. Before removing portions for analysis they were rubbed down to a coarse powder in a large porcelain mortar and mixed as well as possible. This was done quite rapidly, both to avoid possible changes in moisture content and to avoid formation of a pasty mass. Crude fiber: First filtration was made on closely woven linen in a 4-inch Büchner funnel with light suction. Second filtration was on a 11 cm B & A ashless filter paper without suction. Both filtrations were rapid and satisfactory. Starch: Results are multiplied by the factor 1.01 to correct for the dilution of 100 cc of the solution by the 1 cc of sulphuric acid. Sugars: The method of Dubois was followed exactly. It was necessary in extracting with water to break up with a glass rod the compact cake left after centrifuging the last time with gasoline. Inversions were made in the cold (50 ce+5 cc of hydrochloric acid, being allowed to stand over night. All volumes were adjusted at 20° and all polarizations were made in jacketed tube at exact temperatures. The actual polariscope readings (averages of four to five close readings) illustrate the very great influence that small differences in readings have upon the results, in these dilute solutions. In spite of this fact, the method seems to be satisfactory and convenient for judging milk chocolates. The methods are, in my opinion, in as simple a form as possible, and can not well be improved. RECOMMENDATIONS. In view of the small number of collaborators it is hardly possible for the referee to make any formal recommendations based on collaborative work. It is evident, however, that the study of certain of these methods should be continued by the association, especially the caffein estimation and the determination of sugars in chocolate. There would appear to be no reason why the determination of extract in tea as outlined by Doolittle and Woodruff should not be substituted for the cumbersome Krauch method. The experience of the referee on numerous samples of cocoa products suggests that the requirement for filtering and weighing the crude fiber on a a J. Amer. Chem. Soc., 1907, 29: 556; see also Bul. 107, Rev., p. 256. |