baking powders," although the report presents no evidence that this opinion was based on the results of comparative experiments by the Referee Board, or by any investigator. The disagreement between the Referee Board's negative results for absorption of aluminium into the blood (in men), and our own positive findings (for dogs), appears to be an important discordance. If our results in this connection are entirely wrong and the Referee Board's are wholly right, my deductions (quoted above) regarding the possible dangers attending the use of alum baking powder in food for people (based mainly on the toxicity of absorbed aluminium) are obviously unreliable. In reflecting on the possible reasons for the discrepancy between our results and the findings of the Referee Board, I assumed that the negative data for absorption of aluminium, in the experiments by the Referee Board (on men), and our own positive results (on dogs), were correct observations within the limits of accuracy of the procedure followed for each group of experiments. I feared, however, that our own analytic method for aluminium was less. efficient than that used by the Referee Board. On the other hand, it seemed possible that the Referee Board did not take sufficient quantities of blood, in the individual tests, for the detection of small amounts of contained aluminium. I supposed, besides, that dogs might differ from people both in tendency and in ability to absorb aluminium under the conditions of the experiments now in review. After concluding to conduct a further study of the facts in the case, I aimed to project the research along the following three main lines (A-C): A. Ascertain, with the independent coöperation of several colleagues, the efficiency of the aluminium analytic procedure followed by Steel, and by Kahn, in comparison with the method that may now be the "best" for the quantitative determination of aluminium B. Determine the facts pertaining to absorption of aluminium into the blood, and its excretion into the urine, of human subjects, (a) through the agency of the aluminium analytic method found (A) to be the "best," (b) in both small and large volumes of blood and urine, and (c) with the independent collaboration of several colleagues. 8 See foot-note 5. C. Repeat, in at least one series of tests, the essential features of the experiments by Kahn (and Steel), on dogs, but use the aluminium analytic method newly adjudged to be the "best" (A). In order to make this investigation comprehensive and particularly reliable, and completely to forestall any possible suspicion of prejudice on my part in favor of our previous findings, in case they were correct and would be confirmed, I planned to put each section of this research in charge of individuals or groups of workers ("units") that would be geographically, psychologically and professionally independent. I proposed, to each individual or group of workers involved, the solution of specific problems without consultation with, or guidance from, me, and without my divulging to any "unit" the name or names of, or the results obtained by, those in the other "units," while the work was in progress. It was aimed, in short, to make the work of all the "units" coördinated but not concerted. A copy of my requests of, and suggestions to, one of the groups of workers involved, is published below. It illustrates the method of procedure referred to above, as applied to all the groups of workers concerned. "My proposal is, in general, that you join a group of biological chemists in an investigation of certain aspects of the 'baking powder question' and that you coöperate in a study of the comparative values of the best of the available methods for the biochemical determination of aluminium. This proposed study would involve the following conditions: "I. That it be conducted by you (and any assistants you would have) with entire independence of the other workers on the subject, you to be kept in ignorance of their names and results, and vice versa, until the joint completion of the work. 66 '2. Your report to me to be in the form of a finished paper for the BIOCHEM. BULL.; to be printed in that journal after your approval of both galley and page proofs; and to be published nowhere else, prior to its appearance in the BIOCHEM. BULL. "It is intended to make this research far-reaching in scope, accurate in conduct, useful in public service, and creditable profession ally. The independence of each worker is calculated to facilitate chemical accuracy and to insure scientific reliability beyond question. Freedom to report separately each independent part of the research will assure every other desirable consideration. "In this study of the comparative values of available methods for the determination of aluminium, you would be asked to ascertain particularly whether the method used by Steel (Amer. Jour. Physiol., 1911, xxviii, p. 96), and by Kahn (BIOCHEM. BULL., 1911, i, p. 237), was as good as, better than, or inferior to, the method used by Schmidt and Hoagland (Jour. Biol. Chem., 1912, xi, p. 387). This would involve comparisons of determinations of aluminium in standard aqueous solutions and in blood containing known proportions of added aluminium. "In this memorandum I am suggesting merely the most general outlines of the proposed research. You would be free to ascertain the essential facts in your own way as to details. If you endeavor to do the work with every purpose to make an earnest, faithful, and reliable, scientific contribution to this important symposium, you would meet every expectation I could entertain.” This particular phase of the general investigation was begun early in 1915 and has been in continuous progress, in one phase or another, ever since. The original plan has been extended to include a study of several types of baking powders. The four succeeding papers of this series (2-5), in this issue, present the results obtained for section A of the research on the foregoing program, with supplementary comment, in a fifth (6), and a sixth (7), on the method found to be the "best" for the determination of aluminium in biological materials. The four comparative papers (2-5) are published "in the original," in the order of their presentation, without revision of content or adjustment of form. 10 (2) Howe: BIOCHEM. BULL., 1916, v, p. 158; (3) Curtman and Gross: Ibid., p. 165; (4) Steel: Ibid., p. 173; (5) Smith and Hawk: Ibid., p. 183; (6) Gies: Ibid., p. 189; (7) Balls: Ibid., p. 195. 10 Some of the conventional revisions, on a typographical basis, to which manuscripts for the BIOCHEMICAL BULLETIN are usually subjected, were also withheld. SANITARY STUDIES OF BAKING POWDERS 2. A comparison of the method proposed by the Association of Official Agricultural Chemists as modified by Steel, with that described by Schmidt and Hoagland, for the determination of aluminum in organic material. PAUL E. HOWE (Biochemical Laboratory of Columbia University, at the College of Physicians and Surgeons, New York) (Received for publication, July 10, 1915) Introduction. The method used by Steel1 and Kahn,2 for the determination of aluminum in organic material, was compared with that described by Schmidt and Hoagland3 for the same purpose. Steel, after examining various methods for the determination of aluminum in the presence of iron and phosphates, selected the one proposed by the Assoc. of Official Agric. Chem.* as the most accurate He modified this in that the iron was determined in an aliquot portion of the sol. to be analyzed, instead of in the combined, ignited, precipitate of aluminum and iron phosphates. Schmidt and Hoagland studied the conditions under which the Peters method for the precipitation of aluminum in the presence of iron could be used in accurate work. I. The method used by Steel, as described by Kahn, was as follows: Preliminary oxidation of organic material: "The weighed tissue was placed in a Kjeldahl flask and conc. nitric acid sol. added to it. The flask was heated slowly at first and then more vigorously until the sol. became clear, when a moderate excess of nitric acid sol. was added and the liquid boiled down to a small volume. The fluid 1 Steel: Amer. Jour. Physiol., 1911, xxviii, p. 94. 2 Kahn: BIOCHEM. BULL., 1911, i, p. 235. Schmidt and Hoagland: Jour. Biol. Chem., 1912, xi, p. 387. was then treated with a fairly large vol. of conc. sulfuric acid sol. for the expulsion of the nitric acid and for the complete oxidation of any residual organic matter. The sulfuric acid mixture was boiled for at least 2 hr. after it became colorless, in order to eliminate NO2. The residue was then dissolved in water, made up to vol., and the iron and aluminium determined. Determination of iron and aluminum: "Obtain an aliquot portion of the available acid sol. and remove any contained silica. Mix the liquid with sodium phosphate sol. in excess of what is required to form normal aluminium phosphate. Add sufficient ammonium hydroxid sol. to effect complete precipitation of the aluminium phosphate after thorough stirring. Then add hydrochloric acid sol., drop by drop, until the precipitate completely dissolves. Heat the liquid to about 50° C. and mix with it, at that temp., a considerable excess of 50 percent ammonium acetate sol. and also 4 cc. of 80 percent acetic acid sol. As soon as the precipitate of aluminium phosphate (mixed with iron phosphate) has sedimented, collect it on an ashless filter, wash it with hot water, ignite it and then weigh the residue. "In an aliquot portion of the original liquid determine the amount of iron by the Zimmerman-Rheinhardt method. The calculated amount of FePO, is then subtracted from the weight of the mixed AIPO, and FePO,." 4 In the analyses with this method the above procedure was followed exactly as described. It was necessary, however, occasionally to heat the filtrate to boiling in order to obtain a complete precipitation of the phosphates. II. Schmidt and Hoagland give the following description of their method: An aliquot portion of the sol. obtained after the oxidation of the tissues according to the method described by Kahn (see above) is measured into a beaker, the silica dehydrated and filtered off. The filtrate obtained is diluted to about 300 cc. and should contain approximately 2.5 cc. of conc. hydrochloric acid. Tin is precipitated from the hot sol. by hydrogen sulfid and filtered off. Di-ammonium hydrogen phosphate is added to the sol.-0.5 gm. for each 100 mg. of aluminum phosphate present. The sol. is heated and, while hot, 5 gm. 5 Mixer and DuBois: Jour. Amer. Chem. Soc., 1895, xvii, p. 405. Schmidt and Hoagland obtained their sol. for analysis by ashing the tissues and then dissolving the residue. |