SECOND DAY. TUESDAY-MORNING SESSION. No report on saccharine products was made by the referee. REPORT ON MAPLE PRODUCTS. By J. F. SNELL (Macdonald College, Quebec, Canada), Associate Referee. Seven samples of sirup were distributed to collaborators in 1918 and work upon the same samples was continued in 1919. The samples were as follows: No. 1.-Pure, Quebec 1917, Grade I; Canadian lead number, 2.74. No. 6.-Adulterated, prepared from a Quebec 1918, Grade I, maple sirup and a sugar cane product; Canadian lead number of the pure sirup, 3.97. No. 7.-Adulterated, prepared from the same maple sirup used in No. 6 and a "brown" cane sugar. In 1918 collaborators were instructed to study: (1) Preparation of the sample; (2) Winton lead method; (3) Canadian lead method; (4) conductivity value method. In 1919 they were asked to determine: (5) Ash values; (6) malic acid value. In both years they were asked to report refractometer moisture results on the samples as received and to state their judgment as to the purity of the samples, making use of supplementary methods if necessary. Basing his judgment upon the Canadian lead numbers, A. Valin (Laboratory of the Inland Revenue Department, Ottawa, Canada), in 1918, expressed the opinion that Samples 2, 5 and 7 were genuine, the other four probably adulterated. N. C. McFarlane (Macdonald College, Quebec, Canada), in 1919, applying the volumetric lead method1, adjudged Nos. 1, 2 and 5 genuine and No. 7 doubtful. The other collaborators did not venture an opinion. MOISTURE RESULTS. The results of the moisture determinations are given in Table 1. The wide variation in results is not to be emphasized, inasmuch as it may be due partly to actual differences in the portions of the individual 1 J. Ind. Eng. Chem., 1916, 8: 241; J. Assoc. Official Agr. Chemists, 1920, 4: 169. samples included in the various sets of seven. The samples, after they were subdivided and bottled, were sterilized by heating the filled bottles in a covered pan of boiling water. G. J. Van Zoeren (Macdonald College, Quebec, Canada), who prepared the samples, reports that in this process he found it necessary to remove the cork stoppers and cover the bottles with inverted beakers. Inasmuch as sets were sterilized together it is not impossible that different quantities of water distilled out of the various portions of the samples of identical number. The results are arranged in Table 1 according to a suggestion made by Hugh Main, London, England, to whom the results were sent for criticism. Main, not being advised of the possibility of actual differences in the portions of the samples, suggests that probably the control of temperature is the chief source of error. His custom is to work in a room kept as near 20°C. as possible, pass water at 20°C. through the prism jacket of the Abbé refractometer, bring the sample to exactly 20°C. in a small aluminium dish, stirring with a thermometer graduated in fifths or tenths, use the thermometer bulb to transfer the sirup to the prism and then immediately take several readings, bringing the shadow region to the cross lines alternately from above and below. Operating in this way, he finds that his staff agrees in independent readings of the same sample within 0.20 per cent of water and, except for very dark solutions (molasses, etc.) or those that are turbid, he would take this as the maximum allowable amount of deviation from the middlemost result. In Table 1 the results which would be rejected on this basis are printed in italics. In view of the considerable variation between the results of C and F and of P, Q, R and S on identical portions of the sample, there can be little doubt that greater attention should be paid to precision in temperature control. PREPARATION OF SAMPLE. Collaborators were instructed to study the following proposed revised directions and to compare them with the present tentative method: (a) Maple sirup.-Determine the moisture according to 101. If sugar has crystallized out, redissolve it by warming. Shake up any sediment that remains and pour a suitable quantity for analysis (about 100 cc. for all determinations) into a casserole or beaker. Add one-fourth the volume of distilled water. (The advisability of neutralizing with ammonia at this point might well be studied at some future time.) Boil to a temperature of about 104°C. (219°F.). Filter the hot sirup through a plug of cotton wool in the point of a funnel. After cooling, redetermine the moisture according to 101. (b) Maple sugar and other solid or semi-solid products.—(The present report refers to sirup alone. The moisture method for maple sugar may best be made identical with that for some of the other saccharine products, bearing in mind that maple sugar sometimes contains considerable invert sugar.) Determine moisture in the sample in 1 Assoc. Official Agr. Chemists, Methods, 1916, 126. its original condition after thoroughly mixing. For all other determinations, prepare a sirup from about 100 grams of the material by dissolving in about 150 cc. of hot water, boiling to a temperature of 104°C. and filtering through cotton wool as in (a). After cooling, determine the moisture in the sirup according to 10. A few experiments were made by Van Zoeren and the writer on the relative rate of filtration of the hot sirup through cotton wool and through filter paper. Eimer and Amend's "best white", Whatman No. 4 and Carl Schleicher and Schüll's No. 597 papers were used. In all cases, the filtration was very much slower than through the cotton wool. The other collaborators all chose to prepare their samples by the cottonwool method. This seems to be the most satisfactory method in the field and it is, therefore, recommended that the above directions be adopted in place of the present tentative method. Valin in 1918 reported results on the unprepared samples, as well as on the samples prepared according to the proposed revised directions. WINTON LEAD NUMBER. Collaborators were instructed to prepare and analyze basic lead acetate solutions of specific gravity 1.25 (a) from Horne's lead subacetate, (b) from litharge and lead acetate, following the directions given below, and to use these two solutions comparatively in the Winton method and also in the Canadian lead method. PREPARATION OF BASIC LEAD ACETATE SOLUTIONS. (a) From Horne's lead subacetate.-Boil 280 grams of Horne's lead subacetate with 500 cc. of water. When solution is complete except for a slight sediment, allow to cool in the dish or pour off into a Pyrex beaker. Take the sp. gr. at 20°C. and dilute with recently boiled water to a density of 1.25. (b) From litharge and lead acetate.—Weigh 215 grams of normal lead acetate crystals and 65 grams of litharge into a 1-liter evaporating dish. Add about 500 cc. of water. Heat to boiling and boil exactly 30 minutes. Allow to cool in the dish or pour off into a Pyrex beaker. Dilute to a density of 1.25 at 20°C. as in (a). DETERMINATION OF THE ALKALINITY OF LEAD SUBACETATE SOLUTIONS. Pipette 10 cc. of the solution (sp. gr. 1.25) into a small beaker or Erlenmeyer. Add exactly 50 cc. of N/2 oxalic or sulphuric acid. Mix and allow to stand until the precipitate is well settled. Filter into a 250 cc. volumetric flask, washing the precipitate thoroughly with water. Make up to the mark and titrate 50 cc. aliquots with N/10 sodium hydroxid, using phenolphthalein. Half the difference between 50 and the number of cc. of N/10 sodium hydroxid used represents the number of cc. of N/10 sulphuric acid neutralized by 1 cc. of the lead subacetate solution. DETERMINATION OF TOTAL LEAD IN THE LEAD SUBACETATE SOLUTIONS. Pipette 5 cc. of the solution into a 250 cc. flask. Add sufficient acetic acid (about 1 cc. of 30% or 5N acid) to prevent precipitation on diluting, and make up to the mark. Treat 25 cc. aliquots with 25 cc. of water and 1 cc. of dilute sulphuric acid (if 5N, or 2 cc. if 2N). Mix, add 100 cc. of 95% alcohol and allow to stand 3 hours or more. Filter on a tared Gooch, wash with alcohol, dry in an oven and ignite to bright redness in a muffle. Cool and weigh. Multiply the weight of the precipitate by 1.3665 (Pb) to obtain the weight of lead per cc. of solution. CALCULATION OF THE RATIO OF NEUTRAL TO BASIC LEAD. Multiply the alkalinity of the solution (expressed in cc. of N/10 acid) by 0.01036 x10,000). The result represents the basic lead per cc. The difference between the Pb total and the basic lead represents the neutral lead per cc. Calculate the ratio of neutral to basic lead to the second decimal place. The results of the analyses are shown at the foot of Tables 5 and 6 (Canadian lead numbers). It will be seen that Horne's salt yielded solutions a little more variable in lead content but much more uniform in basicity than the litharge and lead acetate. The extreme variations among the five collaborators were: Range of variation in composition of basic lead acetate solution. The results of the Winton lead determinations are given in Tables 2 and 3, the figures being averages of duplicate results. The acetic acid. blank was used in calculating these results. The blanks in which a cane sugar sirup was used in place of the acetic acid did not differ materially from the acetic acid blanks. It will be noted that, although the differences are small, the solution prepared from Horne's salt gives a higher average result on six of the seven sirups. With the following six exceptions, all of the thirty-five results obtained by the individual collaborators on individual sirups are higher with Horne's salt solution than with that prepared from litharge and lead acetate: Valin, Sample 4, both prepared and unprepared; Van Zoeren, Samples 4 and 6; and McFarlane, Samples 3 and 6. As will be seen by reference to Table 6, the solutions prepared from litharge and lead acetate by Van Zoeren and McFarlane were exceptionally basic, having (at the density 1.25) ratios of neutral to basic lead lower than Horne's salt solutions made and analyzed by the same collaborators. It may also be noted that all three sirups in question (Samples 3, 4 and 6) were adulterated sirups. Were it not that results in the opposite direction were obtained by Bryan' with a similarly pre 1 U. S. Dept. Agr. Bull. 466: (1917), 10. pared litharge-lead acetate solution, it might be concluded that in general the 1.25 solutions prepared from Horne's lead subacetate have ratios of about 1.50 to 1.75 and, when diluted, give slightly higher Winton numbers than those prepared from litharge and lead acetate, which normally (at a density of 1.25) have over twice as much neutral as basic lead. For Bryan's similarly prepared litharge-lead acetate solution (his No. 5) the writer calculates the ratio of neutral to basic lead as 1.11. In five out of six pure sirups this gave slightly higher results than a more basic Horne's salt solution (his No. 4; ratio 1.14). In the course of the work on the Winton lead method it was observed by Van Zoeren and the writer that when the filtrate from the lead subacetate precipitate was allowed to stand for a few days it became turbid. This suggested that results might be affected by unduly extending the interval between precipitation and filtration. The results shown in Table 4 indicate that error may arise from this source but the effect of time intervals of more reasonable length has not been investigated. CANADIAN LEAD NUMBER. Weigh the quantity of sirup containing 25 grams of dry matter, transfer to a beaker, add 50-75 cc. of water, boil gently for 2-3 minutes, transfer to a 100 cc. flask, cool and make up to the mark. Pipette 20 cc. of this solution into a large test tube, add 2 cc. of lead subacetate solution (sp. gr. 1.25) and mix. Allow to stand 2 hours, filter through a tared Gooch, having an asbestos mat at least 3 mm. thick, wash four or five times with boiling water, dry at 100°C. and weigh. Multiply the weight of the dry precipitate by 20. In the collaborative work of 1917, it was noted that Valin obtained lower results on all sampels than did Van Zoeren and the writer. After the report was completed, an interchange of solutions was made between the two laboratories and the following results obtained: Comparison of Canadian lead numbers obtained in 1917 with différent solutions of basic lead acetate. * Prepared in Food and Drugs Laboratory, Inland Revenue Department, Ottawa, Canada. † Result obtained in October. Prepared in Macdonald College Laboratory, Macdonald College, Quebec, Canada. |