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phuric acid formed), and heat to boiling till nitric acid fumes are all expelled. Cool, make up to mark with distilled water, mix thoroughly, filter through a dry filter and take 50 cc of the filtrate (0.5 gram) for the determination of arsenic oxid. Transfer this 50 cc portion to a 400 ce Erlenmeyer flask, dilute to about 100 cc with water, add 2 to 3 grams of potassium iodid and 5 cc of concentrated sulphuric acid, heat to boiling and evaporate to about 40 cc. Cool, dilute to 150 cc to 200 cc and add approximately tenth-normal sodium thiosulphate just to disappearance of color caused by the free iodin. In case the solution is slightly colored from iron or incomplete oxidation of the organic matter, add the thiosulphate until nearly colorless, then add a few drops of starch paste and continue adding the thiosulphate slowly until the blue color just disappears. The exact end point can easily be obtained in this way. Neutralize immediately with sodium carbonate, make slightly acid with dilute sulphuric acid, and when all lumps of sodium carbonate are dissolved add sodium bicarbonate in considerable excess. Titrate with twentieth-normal iodin solution in the usual way, using starch solution as indicator. Subtracting from this the number of cubic centimeters of iodin solution corresponding to arsenious oxid as determined by Method I, gives the number of cubic centimeters of iodin solution corresponding to the arsenic oxid (As05) in 0.5 gram of the sample.

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R. J. Davidson: There is no great difficulty in working the London purple by Method IV for arsenic oxid. It is perhaps a little more troublesome and you have to use another method for getting the arsenious oxid. I believe Method III, provided it gives satisfactory results, is the simplest method, both determinations being made from the same weighed sample.

R. W. Thatcher: Davidson's modification (Method III) makes the end point somewhat easier to determine. The modification suggested by the referee does not seem to me to offer any advantage over the official method, since the yellow color left after oxidation with nitrate mixture obscures the end reaction as badly as does the original color and has the disadvantage of requiring a separately weighed sample for the determination of the arsenic in arsenious form.

C. D. Woods: I would emphasize the fact and recommend that it be included in directions for insecticide work, that this kind of work is difficult for a beginner and that several preliminary determinations should be run before a man new to this work attempts to report results.

As has been the case in previous years, the results on arsenic oxid are very unsatisfactory, there being a difference of over 4 per cent between the highest and lowest determinations by Methods I and III, and over 2 per cent difference by the same method by different analysts. Methods II and III give lower results than Method I, but there does not appear to be any uniformity in the amount that these methods fall short, the determinations made by different analysts and even those by the same analyst at different times sometimes agreeing with those made by Method I and at others showing a variation of several per cent. Why this is so has not as yet been determined, but is under investigation. It is the referee's opinion that on precipi

tating the coloring matter with sodium carbonate a varying amount of arsenic is carried down in the precipitate.

The determinations made by Method IV, while not agreeing as closely as might be desired, are close enough to justify a more extended trial of the method in the hands of different analysts. The writer has found it very satisfactory and, when properly carried out, a perfectly clear solution can almost always be obtained. Of course it is desirable to be able to determine both forms of arsenic on the same solution, but if it is found that this can not be done accurately this objection to the method becomes of minor importance.

LEAD ARSENATE.

The methods used for lead arsenate were proposed by Haywood at the meeting of the association in 1906 and were tried last year. They may be found in Bureau of Chemistry Bulletin 105, page 165; also Bulletin 107, revised, page 239.

The sample sent out for the work was made by the referee from C. P. di-sodium arsenate and lead acetate.

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C. D. Woods states that in the determination of total arsenic oxid it was not found necessary to add thiosulphate to use up free iodin because if care is used in boiling the solution a colorless point is easily obtained.

The results on lead arsenate are not so uniform as might be desired, particularly on total lead oxid. However, the difference between the highest and lowest determination of arsenic oxid is only 3 per cent of the total amount present and for lead oxid 5 per cent of the total amount present. The method is certainly the best that has thus far been proposed and if carefully followed good results should be obtained.

SODA LYE.

METHOD I.—This is the precipitation method, and may be found in Circular 10, revised, page 8, and Bulletin 107, revised, page 31.

METHOD II.-This is the same as Method I except that the titration for hydroxid is made without removing the barium carbonate precipitate.

The acid potassium sulphate method was not submitted for trial, as satisfactory results had not been obtained by it in previous years and the association voted that it be dropped, as recommended by the referee in 1907.

As it was desired to send out samples containing considerable carbonate, and such were not at hand they were prepared as follows: The sample bottle was weighed and into this was weighed 2 grams dry sodium carbonate C. P. then, as rapidly as possible, 18 grams of commercial sodium hydrate. The bottles were then stoppered and sealed. The analyst was directed to dissolve the entire content of the bottle in carbon dioxid-free water, make up to 2,000 cc and use 50 cc portions for the titrations (0.5 gram sample). The results submitted have been multiplied by two and reported in per cent in the following table:

Soda lye.

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The results on sodium hydroxid are very good. As expected, Method II gives slightly higher results for hydroxid and lower on carbonate than Method I. The difference, however, is small. The referee determined carbon dioxid in a portion of the sample gravimetrically and found 11.62 per cent and 11.71 per cent calculated as sodium carbonate.

Using these two indicators in the same determination, as is done in this method, the tendency would always be to high results on sodium carbonate. Phenolphthalein, being more sensitive to acids, becomes colorless immediately when the solution is neutral, while with methyl-orange the acid must be in slight excess to develop the pink color, the excess required depending on the amount of indicator used and the depth of color titrated to. A blank should be made, using the same amount of water and indicator, and deducted in each case when methyl-orange is used. For the determinations in the second report in the table the analyst used normal acid. This may account for the results in sodium carbonate being high, as 0.1 cc normal acid is equivalent to over 1 per cent sodium carbonate, when operating on 0.5 gram of substance.

FORMALDEHYDE.

Two samples were sent out for analysis, No. 1, a strong solution to be worked by the modified hydrogen peroxid method, and No. 2, a dilute solution to be worked by the cyanid method, both found in Bulletin 107, revised, page 33.

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Sample

No. 2. Method II.

Per cent.

Per cent.

3.92

36.81

3.98

36. 71

3.92

36.64

3.83

36.46

3.70

3.98

37.00

3.84

36.93

36.76

3.90

COMMENTS AND DISCUSSION.

R. J. Davidson says: "I believe it would be well to state the amount of dilution necessary in Method II and not say, as the method does, ‘a weighed quantity of the dilute formaldehyde solution.' The directions should be more specific."

The results on formaldehyde are very good. Method I is an excellent method for strong solutions, and Method II for dilute solutions, containing preferably not over 5 per cent. Even solutions of the latter strength must be diluted before making the determinations.

The referee is in favor of the recommendation made last year and referred to again in Mr. Davidson's report, that more specific directions should be given this method. If, instead of the words "a weighed quantity of the dilute formaldehyde solution," line 8, the following were inserted, “a weighed quantity of the formaldehyde solution containing not over 2 cc of a 1 per cent solution or the equivalent," it would make the method clearer and sufficiently explicit.

SULPHUR DIPS.

The method is that of Avery and is given in Circular 10, revised, also Bulletin 107, revised, page 34 The sample submitted for analysis was prepared in the laboratory by boiling together lime and sulphur according to the regular formula for the limesulphur spray mixture.

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The results are all very close, the greatest difference being only 0.25 per cent. This method has also given satisfactory results in past years.

In view of the fact that this report was not presented at the meeting of the association, no recommendations will be made at this time.

PRESIDENT SNYDER'S ADDRESS: THE TRAINING OF THE

AGRICULTURAL CHEMIST.

I have selected as the subject of the president's address for this, the twenty-fifth annual convention of the Association of Official Agricultural Chemists, "The Training of the Agricultural Chemist."

Any society or organization in order to be effectual and progressive must look well to its membership. Our society has been most fortunate in this respect, and it is to be hoped its ranks will continue to be filled with the same class of earnest, energetic workers as are here to-day. During the past quarter of a century this organization has accomplished most excellent results. I believe, however, that it has only entered upon its career of usefulness. Much credit is due to the founders for the high ideals of the association and for the cultivation of the true scientific spirit. Many of them

received their training in the great European laboratories, where they were students of Liebig, Fresenius, Voit, Hoffman, and Pasteur, and they have planted in this country the seed of true agricultural research. Most of the older members have relinquished their labors, and the work of the society may now be said to be in the hands of the second generation, who, it is hoped, will meet with as much success and foster the same spirit and ideals.

Originally agricultural chemists were in a way self-educated. They secured what knowledge they could of general and analytical chemistry and then applied it to the solution of agricultural problems. Naturally the work was largely analytical. "What does this substance contain?" was and is to-day the quest of the chemist. During the past few years, however, the domains of agricultural chemistry have been greatly enlarged and there is probably now no other branch of chemistry that calls for so wide a training. Organic, inorganic, industrial, physical, physiological, and sanitary chemists have definite channels within which their activities are confined, while the agricultural chemist must necessarily include in his domain a large portion of all of these. In dealing with the soil an extended knowledge of both inorganic and organic chemistry as well as of physical chemistry is requisite. Our knowledge of soils is necessarily much restricted because the chemistry of the silicates is so imperfectly understood, and so in the analysis of plant and animal substances and the interpretation of the results our knowledge is likewise very limited. While the data gained from the analysis of foodstuffs is exceedingly valuable, I do not believe that it is as much so as it is destined to be, and while chemistry is one of the most useful of the sciences in the study of agricultural problems, it is capable of being made still more valuable and useful.

One of the chief functions of the agricultural chemist is to correctly analyze agricultural products. In order to do this methods of analysis based upon rational principles must be devised, and this is one of the principal features of the work of this association. It is scarcely necessary for me to dwell upon its importance. Correct methods of analysis are essential, as without these chemistry would be entitled to no higher rank than alchemy. I do not believe that the importance of the development of correct methods for the analysis of agricultural products is as fully appreciated by experiment station workers as it should be. A large amount of the work that has been done is destined to be discredited and discarded because of errors in methods employed. Some of our experiment stations have been too impatient to secure immediate results and have not paid sufficient attention to methods of investigation. The study of the methods for analysis of foods and agricultural products can well be continued as the most prominent feature of this organization.

With the advance that is being made in general science and the greater recognition given agriculture, more extended provision should be made for the education and training of the prospective agricultural chemist. There are many institutions that offer excellent four-year courses in chemical engineering and other branches of chemistry leading to degrees. I know of no American institution where such a course is given in agricultural chemistry. Has not the time arrived for the establishment, in some of our institutions of courses of study having for their object the training of agricultural chemists? Certainly the importance and magnitude of the field would suggest the need of such courses. I shall not discuss the subjects that could most consistently form a part of the curriculum, but there should be a correlation of the different sciences blended with general and technical chemistry. As matters now stand, it is generally necessary for an experiment station to secure as assistants young chemists who have had but little training in analytical chemistry and give them special training in agricultural analysis. The experiment stations have to train their own assistants and by the time they have become reasonably proficient another institution or some industry offers a higher salary and then new assistants must be initiated, the process in some cases being repeated several times a year. Our

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