TABLE 2.-Moisture determinations obtained by drying in a vacuum for varying periods.

HEMPLE DESICCATOR.

In Table 2 the results obtained by drying in the Hemple and Scheibler desiccators are given. The results obtained after standing 7 days in the Hemple desiccator compare very favorably with one another, though in a few instances maximum results are obtained even with 5 days' drying. The maximum results obtained for 7 days' drying are 11.56 per cent for sample No. 1; 10.86 per cent for No. 2; 14.73 per cent for No. 3; and 8.30 per cent for No. 4. The average results are, for No. 1, 11.28 per cent; No. 2, 10.49 per cent; No. 3, 14.50 per cent; and No. 4, 7.90 per cent.

In that part of the table showing the results obtained in the Scheibler type of desiccator the maximum figures show uniformly higher results, being nearly 0.2 per cent higher than the maximum figures obtained in the Hemple form. Further, as the determinations were carried on in this case for periods of 12 and 20 days, the results indicate that drying for 7 days extracts the greatest amount of moisture from the samples. In sample No. 1 there is a gain in weight of the sample after 7 days' drying, No. 2 and No. 3 remain practically constant, while sample No. 4 shows a gain. TABLE 3.-Moisture determinations obtained by drying at a temperature of boiling water in a slow current of dry hydrogen.

Table 3 gives the results obtained by drying in a current of dry hydrogen at the temperature of boiling water. Determinations were made in duplicate and triplicate, the average only being given. Weighings were made at the end of each hour's drying and continued until the sample gained in weight. The maximum time of drying was 8 hours in the case of sample No. 1, while 4 hours' drying sufficed for sample No. 3. TABLE 4.-Comparison of maximum moisture determinations given by each method.

In Table 4 the maximum results obtained by each method are arranged for comparison. In the samples containing the largest amount of starch, Nos. 1 and 3, the vacuum method gives the highest results, while in the more complex samples, as No. 2, wheat flour, and No. 4, shredded wheat, drying in partial vacuum in a current of dry air gives the highest results. It is not to be inferred from this that the method giving the highest results necessarily gives the exact percentage of hydroscopic moisture. Whether material other than water volatilized at the temperature of 100° C., to which the samples in partial vacuum were exposed, must be determined by a future study of this subject.

It is evident that in a vacuum of 0-5 mm of mercury, which is maintained in the desiccators, there would always be a tendency to establish an equilibrium, the rapidity with which it would be established depending on the volatility of the substances. Under such conditions, there must be a small quantity of vapors of sulphuric acid at

all times within the desiccator, which may exert a slight influence on the determinations.

The fact that determinations made in the Scheibler vacuum desiccator give maximum results at the end of 7 days' drying and then show a gain in weight in nearly all cases after that period, led to the determination of total sulphur in the original samples and in the samples which had stood 12 and 20 days in the desiccator. The sodium peroxid method was employed, the fusion being conducted in nickel crucibles. Three-gram samples were employed in duplicate for the determinations in the original samples, while the vacuum samples were approximately 1 gram. The duplicate determinations agreed closely throughout and a blank on the maximum quantity of sodiu.n peroxid used to complete fusion did not give any sulphur.

The results are given in Table 5, and with the exception of No. 3 the figures are quite striking, showing that this is a factor to be given some consideration, particularly in reference to time of drying. Sample No. 3, which, it will be remembered, is nearly pure starch, gave the highest percentage of water by this method and evidently did not, during the time stated, absorb any of the sulphuric acid. On the other hand, No. 1, rice flour, also contains a high percentage of starch, but shows quite an increase in sulphur content. Sample No. 2 shows an increase of 0.048 per cent during the 12 days, while No. 4 shows an increase of 0.098 per cent. The table also shows that the maximum gain in sulphur takes place within the first 12 days, the results from standing 20 days being practically the same, and very good duplicates of the first set.

TABLE 5.-Sulphur in samples before and after drying in vacuum desiccator.

From the results of the present year's work it is evident that the vacuum method is worthy of careful consideration. The application of the method to a greater variety of materials will secure valuable data as to its value for the determination of water in foods. Recommendations with this end in view and the study of any modifications which may facilitate drying are accordingly made.

RECOMMENDATIONS.

It is recommended that the study of the vacuum method for the determination of water be continued next year.

That the methods employed for study shall be:

The present vacuum method in either the Hemple or Scheibler type of desiccator. The vacuum method with any modification which may facilitate drying, as the introduction of phosphorus pentoxid as a drying agent.

Drying in a partial vacuum in a current of dry preheated air and inert gases.

The report was referred to Committee C on recommendation of referees.

31104-No. 105-07-5

REPORT ON CEREAL PRODUCTS.

By A. MCGILL, Associate Referee.

The definitions of cereal products authorized by the Secretary of Agriculturea are carefully framed so as to employ no words in regard to whose meaning there can be any doubt. Thus, in the definitions of flour and meal, no mention is made of gluten nor of proteids; nor is any minimum of proteid nitrogen fixed. In our present state of imperfect knowledge this is well, but it is undoubtedly to be desired that such a well-known and widely used term as gluten could be given a meaning of sufficient precision to permit of its being employed in connection with flour. It is the word best known to the miller and the baker as representing the valuable and distinctive proximate component of wheat flour. The separation of gluten, the determining of its total amount and of its qualities, are everyday proceedings in all technical laboratories, and especially in such as make a specialty of cereal work.

In the appended notes the recent literature of this subject has been abstracted, presenting very briefly the novel features in the hope that such a definite conception of gluten may be reached as will permit of formulating an acceptable definition.

GLUTEN.

CONDITIONS AFFECTING GLUTEN ESTIMATION.

The term gluten is applied to the residue obtained by kneading a dough from wheat flour in a stream of water in such a way as to wash away most of the starch, or until the wash water remains practically clear. The operation is incapable of yielding exact results, and when carried out as described can be regarded as affording merely approximate information about the samples of flour tested. Arpin has shown that the percentage of gluten obtained varies with the temperature of the wash water, being higher with warm than with cold water. Thus, on a sample of wheat flour, washed with water at 5° C., he found 7.83 per cent gluten; at 15° C., he found 8.08 per cent, and with water at 25° C. he found 9.24 per cent.

Again, if washing be continued after the removal of the starch, a very considerable loss of gluten occurs. For only five minutes' extra washing he found a loss of 21 per cent moist gluten (0.9 per cent dry).

Balland has shown that the amount of gluten obtained depends to some extent upon the length of time that the cake of dough is allowed to lie before being washed; and Arpin, while corroborating Balland's observation, shows that the "hardness" of the water used in washing has a great influence on the amount of gluten obtained. He found as much as 4.7 per cent increase (dry gluten) when hard water was employed. Recognizing the various factors which affect the yield of gluten, Fleurente advises the use of water containing 0.1 gram of calcium carbonate per liter (of course dissolved as bicarbonate) at a temperature of 16° C., kneading the dough for 11 minutes and washing for 2 minutes, finally drying at 100°-105° C. He has found that distilled water reduces the yield of gluten; also that lime as sulphate or chlorid gives a lower yield of gluten than when present as carbonate. Sodium chlorid has a like result. Fleurent also advises that old or acid flour be made neutral with bicarbonate of soda before the determination of gluten.

a Circular 19 of the Secretary's Office, 1906, Standards of Purity for Food Products. Ann. chim. anal. appl., 7: 325-Abst. J. Soc. Chem. Ind., 1902, 21: 1417.

c Ann. chim. anal. appl., 7: 416-Abst. J. Soc. Chem. Ind., 1903, 22: 168.

d Loc. cit. 7: 376-Abst. J. Soc. Chem. Ind., 1902, 21: 1560.

e Comptes rendus, 1905, 99-Abst. J. Soc. Chem. Ind., 1905, 24: 155.