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0.15 per cent. below the average by the Kjeldahl method. On samples rich in nitrogen, such as cotton-seed meal, there seems to be great liability of obtaining results too low, unless small quantities of the substance are used and due care exercised in the combustion.

Five chemists report results by the Ruffle method. On sample No. 1 the average is 15.88, the theory 15.91; a difference of 0.03 per cent.

For sample No. 2 (cotton seed meal) the Kjeldahl method was used by fifteen chemists, the average of the results giving 7.50 per cent. nitrogen. The results are highly satisfactory; nine coming within 0.1 per cent. of the average, and all within 0.25 per cent.

Fifteen of the seventeen chemists used the Kjeldahl method modified for nitrates for samples Nos. 1 and 3. On sample No. 1 the average of all the results is 15.92, the theory 15.91. On sample No. 3 the average is 3.54, the theory 3.55.

The average on sample No. 1 ir cludes three results, which are nearly 0.5 above the theory. In making conclusions as to the accuracy of the methods it would be better to leave these three results out of the average, as they are so far out of the way as to reflect inaccuracy or carelessness on the part of the chemist rather than the method. Doing so, the average per cent. of nitrogen found in sample No. 1 is 15.86; a result which is 0.05 per cent. below the calculated amount. The highest result is 16.16 per cent., the lowest 15.74 per cent., if we do not include the result from Arkansas, which we should not, as zinc filings were used instead of zinc dust in this determination. The difference between highest and lowest results is 0.42 per cent., or a difference of only 2.6 per cent. of the average. Fifty-five per cent. of the analysts come within 0.1 per cent. of the average, and 91 per cent. within 0.25 per cent.

The results obtained prove, I believe, conclusively that the modified Kjeldahl method is an accurate and reliable oue for the determination of nitrogen in fertilizers containing nitrates. On pure nitrates the results are invariably a trifle low. The loss seems mostly to occur when the zinc dust is added. For this reason zinc dust is objectionable. It is objectionable also in giving so much zinc sulphate to contend against in the distillation. Dr. Burney states that the great amount of salts present causes his flasks to break frequently in the distillation. This has also caused us trouble to some extent. Working on the theory that that HS would complete the reduction as well if not better than nascent hydrogen, Prof. A. M. Peter and I made a series of experiments, using zinc sulphide in place of zinc dust. The results on pure potassium nitrate containing a trace of water, giving the theoretical per cent. of nitrogen 13.83, were as follows:

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On pure potassium nitrate-Continued.

[2. Series. Two grams zinc sulphide used in place of three grams zinc dust.-Results.]

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[2. Series. Two granis zinc sulphide in place of three grams zinc dust.-Results.]

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I would recommend that the samo methods used this year be the official methods for the ensuing year, with some slight modifications, as follows:

1. As shown by the factors sent the reporter-the standard acid, while closely agreeing in many cases; varies somewhat in others. In order to correct any inaccuracies, if possible, in testing the acid it is recommended that the paragraph describing the standardizing the acid be so changed as to read as follows:

(1) Standard hydrochloric acid whose absolute strength has been determined.

(a) By precipitating with silver nitrate and weighing the silver chloride, as described in Crooke's Select Methods, page 571.

(b) By potassium tetroxalate, which has been purified by recrystalizing three times.

(c) By sodium carbonate.

(d) By determining the amount neutralized by the distillate from a weighed quantity of pure ammonium chloride boiled with an excess of sodium hydrate.

Half normal acid, i. e., containing 18.23 grams hydrochloric acid to the litre, is recommended.

2. Under the Kjeldahl method, page 63, Bulletin No. 19, Division of Chemistry, U. S. Department of Agriculture, under “(6) granulated zinc," add "or pumice stone, to be added to the contents of the flask in distillation when found necessary in order to keep from bumping."

3. On page 65, under "distillation," third line, after "granulated zinc," add "or pumice stone if found necessary in order to keep contents of flasks from bumping." In the Kjeldah method, modified for nitrates, it is recommended to use 2 grams of zinc dust instead of 3 grams as hitherto. A number of determinations have been made with 2 grams of zinc dust, and in every case the results show that the amount is sufficient.

In the case of sample No. 1 several determinations with 3 grams of zinc dust gave an average loss of 0.11 per cent. N., while parallel experiments with 2 grams zinc sulphide gave results as follows:

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The object of course is to use as little zinc dust as possible to avoid excess of salts. With 1 gram of zinc dust the reduction is not complete, as may be seen by the following results:

One gram zinc dust used; per cent. nitrogen found; sample 1.

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It is recommended, also, that the reporter, when sending out samples for next year's determinations, request chemists to try zinc sulphide in place of zinc dust. In such case, 1 gram salicylic acid and 2 grams zinc sulphide are the proportions necessary. It was moved that the report be accepted. The motion was carried. At 12.30 a recess was taken until 2 o'clock.

AFTERNOON SESSION, WEDNESDAY.

The convention was called to order by the president at 2 p. m.

The president stated that the reporter on cattle-food analysis wished to bring up one point which had been omitted in the discussion of yesterday; if there was no objection the floor would be accorded to him for this purpose.

Mr. Caldwell said he would recommend the following:

That the reporter on the analysis of cattle foods be requested to send out a special sample of a cereal preparation to be analyzed by the Dragendorff method, any directions for the same to be sent by the reporter with the sample.

It was moved that the recommendation of Mr. Caldwell be accepted and adopted.

The motion was seconded and carried.

The president said that in the resolution adopted in the morning session providing for the appointment of a committee to consider the report upon ways and means for more thorough chemical study of foods and feeding stuffs the number of persons composing such committee was not stated. It would probably be well to attend to that point

now.

Mr. Jenkins moved that the said committee should consist of five persons, to be appointed by the president.

The motion was seconded and carried.

The chair appointed Messrs. Atwater (chairman), Caldwell, Jenkins, Jordan, and Wiley.

The president stated that the discussion of the report upon nitrogen was now in order. The reporter had made certain recommendations which would be taken up in order and passed upon by the association.

Mr. Scovell said that it was recommended to insert after the words "silver chloride," on page 63, under the head of "Kjeldahl method," second line, the words "as described in Crookes' Select Methods (last edition), page 571."

He would suggest that the determinations be made by precipitating and weighing the silver chloride, and that this be done in the manner described in Crookes' last edition.

It was moved that the recommendations of the reporter be adopted. The motion was seconded and carried.

Mr. Scovell said that he would also recommend, referring still to page 63, the leaving out of (b) and (c) down to "sodium hydrate," and the insertion in place thereof of the following: "(b) by potassium tretroxalate, which has been purified by recrystallizing two or three times; (c) by sodium carbonate, as described in Fresenius' Quantitative Analysis, second American edition, page 680."

Mr. Jenkins said that he would not oppose the introduction of the tretroxalate, and did not know that it was necessary to retain the others, but it seemed to him that there was a certain advantage in it. The

standard acid was the basis for all operations, and too much care could not be taken in establishing that standard very accurately and beyond the preadventure of a doubt. A coast-survey man would hardly be willing to depend upon one or two observations for the length of his base line, and no one should be satisfied with a single method or with two methods if more can be employed in so important a matter as this. He always used four or five methods and compared them on his acid, and until the results agreed perfectly he did not feel safe.

Mr. Scovell said that he did not believe that the first of the methods was equally accurate with the other two, and he thought that two accurate methods were certainly better than three methods, one of which was not accurate. In sodium carbonate the results were found to be lower, and on that account it might be well to go on and say use calcium carbonate in place of sodium carbonate. He considered the sodium-carbonate method an inferior way of getting at the required stand

ard.

Mr. Jenkins moved that instead of omitting the words recommended by the reporter to be omitted the same be retained and the words "and tretroxalate of potassium" be inserted.

Mr. Caldwell said that he would prefer to have the tretroxalate put second, before the carbonates, as he believed it to be a very safe and easy method of testing.

Mr. Scovell accepted the amendment.

The motion was seconded and carried.

Mr. Scovell said that he would recommend, referring to page 63, under the head No. 6, the substitution of pumice stone in the place of granulated zinc. He did not insist that pumice-stone be adopted, but would simply recommend it as being better than zinc. He had used granulated zinc in distillation, and had taken about a dozen blanks with some soda which he had and found that the blanks did not agree perfectly; by leaving out zine and putting in pumice stone in the manner described by Mr. Wiley the blanks were so even that he could not tell the difference in the sodium neutralized, except in one case he got one cubic centimeter deci-normal soda more. He feared that it might break more flasks than the zinc would. It seemed to bump around, although he would not be certain in regard to that. He would like to ask whether others had experience in that direction. Personally he thought pumicestone much better than granulated zinc. However, he would change his recommendation, and would say for this year zinc or pumice stone. Mr. Voorhees said that he had found it unnecessary to use zinc in his distillations, and supposed that a great many others would say the same." He found when he had used zinc that no better results were obtained; therefore, he had discarded it entirely. For two years he had used no zinc in the final distillation; his distillations were very good, indeed, and he did not think that he had lost a flask this year from bumping of solutions.

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