TABLE 4.-Comparison of modified and Smith methods for total potassium. a Duplicates not reported. COMMENTS OF ANALYSTS. P. E. Brown: The magnesium nitrate method is undoubtedly quicker and easier of manipulation than the peroxid fusion method. It has the advantage that there is not nearly such a large amount of silica to get rid of, as it was found necessary to dehydrate three or four times with the peroxid fusion method. Then, too, in the first operation of the fusion method there seems to be an uncertainty of reaction while avoiding fusion, which is of course eliminated in the other method. You will notice from the results that the agreement is fair with a tendency for the new method to give slightly higher results. However, if the first determination in Soil I by the fusion method is eliminated, the agreement is much better. On the whole the magnesium nitrate method seems to me to be undoubtedly superior to the other. W. P. Kelley: I find the magnesium nitrate method as outlined by you to be a very simple and convenient scheme for determining the phosphoric acid in soils; and while I have not had an opportunity to compare this method with others, I have no doubt that the results are reliable. RECOMMENDATIONS. The work done this year, while not as extensive as the referee had wished, still warrants in his opinion three conclusions, especially when it is remembered that work along the same line last year and the year before is mainly concordant in the matter of results: First, that the modified J. Lawrence Smith method for total potassium compares very favorably with the regular method and is somewhat shorter; second, that the sodium peroxid fusion method for total phosphorus gives good results, but the manipulation presents some difficulty, and the time required for making the determinations is a disadvantage; third, that the magnesium nitrate method gives uniformly as good results for total phosphorus as the sodium peroxid fusion, and is quick and easy of manipulation. With these facts in view, the referee would make the following recommendations: (1) That the modified J. L. Smith method for total potassium be adopted as an optional method of this association. (2) That the sodium peroxid fusion for total phosphorus be adopted as an official method. (3) That the magnesium nitrate method for total phosphorus be adopted as a provisional method of this association and be further tested. REPORT ON THE DETERMINATION OF CALCIUM CARBONATE IN SOILS. By JACOB G. LIPMAN, Associate Referee. Systematic determinations of calcium carbonate in cultivated soils seem highly desirable in view of its important functions in crop production. Unfortunately, there is no unanimity of opinion among chemists as to the methods best adapted for this work. When the proportion of calcium and magnesium carbonates exceeds 1 per cent, fairly accurate determinations may be made by the liberation of carbon dioxid and its absorption and weighing in potash solutions. But when the proportion of carbonate is small, as is true of so many of our soils, the quantity of carbon dioxid which remains in solution in the acid is very large in proportion to its entire amount. This source of error has frequently been commented upon and has led to several more or less successful attempts to correct it.a The associate referee on soils thought it advisable, therefore, to outline some cooperative work on one or two promising methods for the determination of carbonates in soils. Samples of two different soils were sent to eleven members of the association who had signified their willingness to cooperate in the testing of soil-analytical methods. It was suggested that determinations of carbonates be made in the samples by Knorr's method as described in Wiley's Agricultural Analysis. Where possible, the results secured by Knorr's method were to be checked by the method described by Amos in the Journal of Agricultural Science.c The samples were sent out early in September, and analyses were made and reported by W. B. Ellett of the Virginia station, by Percy E. Brown of the New Jersey station, and Ernest Van Alstine of the Illinois station. Mr. Van Alstine's data were transmitted to the associate referee by Mr. Hopkins. Mr. Ellett and Mr. Brown used Knorr's apparatus for the determination of the carbon dioxid. Mr. Van Alstine employed the method regularly used at the Illinois station and consisting of the liberation of the carbon dioxid "by boiling with hydrochloric acid and ascertaining the quantity of carbon dioxid evolved by measuring before and after absorption by a caustic potash solution.” The results were as follows: a See Hall and Russel, A Method for Determining Small Quantities of Carbonates, Transactions, J. Chem. Soc., London, 1902, 81:81. b Vol. 1, p. 338. c 1905, 1:322. The results submitted by Ellett and Brown agree very satisfactorily. Those submitted by Van Alstine are markedly lower, especially in the case of soil No. 2. Apparently the amount of carbon dioxid which remained in solution in the latter work is the cause of the lower results. Evidently Knorr's apparatus is efficient for the determination of comparatively slight amounts of carbonates; however, it is desirable that further work be done along this line, and the associate referee would therefore recommend that it be continued with certain modifications for at least another year. REPORT ON POTASH. By B. B. Ross, Referee. The work on potash for the past year has included cooperative tests of the regular official method in comparison with the phosphomolybdic volumetric method, and, in addition, the referee, associate referee, and some cooperating chemists have made comparative tests with some special methods which will be described in the latter portion of this report. Twenty laboratories expressed a desire to take part in the cooperative work on potash samples, but reports were received from only eight laboratories. Two samples were sent out for analysis to each laboratory taking part in the work, sample No. 1 being high-grade commercial sulphate of potash, while sample No. 2 was a mixed fertilizer, the ingredients of which were acid phosphate, cottonseed meal, dried blood, potassium chlorid, and a small amount of magnesium sulphate. The following instructions with regard to the work were sent out to all cooperating chemists, the details of the volumetric method being those given by the referee for 1906 and 1907, Mr. A. L. Knisely, who had given much time and attention to a study of the phosphomolybdic method. OUTLINE OF ASSOCIATION POTASH WORK. Sample No. 1. Commercial sulphate of potash. Sample No. 2. A complete mixed fertilizer, the nitrogen of which is derived from cottonseed meal and dried blood. Potash in these samples should be determined both by the official method and the proposed volumetric method involving use of phosphomolybdic acid. Reagents. Nitric acid.-50 cc of nitric acid (1.40 sp. gr.) in 1,000 cc of water. Phosphomolybdic acid solution.-100 grams of phosphomolybdic acid (Kahlbaum's preferred) in 750 cc of water and 250 cc of nitric acid (1.40 sp. gr.). This solution must be freshly prepared—not over three or four days old before using. If properly made the evaporated residue from a portion of this solution is never white and readily redissolves in the dilute nitric acid solution in the cold. Standard solutions.-Standard caustic potash and nitric acid prepared for volumetric phosphoric acid diluted to 2 volumes. One cubic centimeter of this potassium hydroxid solution is equal to 0.812 mg of potassium oxid. Determination. Transfer 10 cc of solution to a platinum dish, add 0.25 cc of sulphuric acid (1 to 1). Evaporate to dryness and ignite to whiteness. Dissolve residue in hot water plus a few drops of hydrochloric acid and transfer to a tall 200 cc beaker, add 30 cc phosphomolybdic acid solution and slowly evaporate to complete dryness on top of a steam bath. It requires approximately 22 mg of phosphomolybdic acid, in order to have an excess, for each milligram of potassium oxid present. Add 30 cc of nitric acid wash to the dried residue and stir thoroughly in the cold, with a grinding motion with a policeman, allow to settle a moment and decant supernatant liquid at once through a gooch crucible packed with moist filter paper pulp, approximately one-sixteenth inch in thickness. Wash twice by decantation with sodium nitrate wash, transfer precipitate to a gooch and wash with sodium nitrate wash until acid free. Transfer gooch to casserole, run in excess standard alkali solution and add phenolphthalein. Heat to boiling and titrate excess alkali with standard acid. Some samples of asbestos seem to hold or "fix" some of the excess acid, making the gooch filter very hard to wash acid free. Hence it is suggested to use a paper pulp filter. It is also desirable to make comparative tests, employing the usual asbestos filter. If excess of phosphomolybdic acid has been used, the dried residue has a reddish hue. If excess has not been added the residue is bright yellow. Residue should not appear white. In each case, run blanks to ascertain corrections to be made for impurities. It is also desired that in sample No. 1 determinations of potash be made, not only by the official method (which provides for direct evaporation of the solution without addition of ammonia and ammonium oxalate), but also by the method applicable to mixed fertilizers, adding ammonia and ammonium oxalate, followed by evaporation and subsequent ignition with sulphuric acid. Several chemists have urged that this latter method of procedure be tried, as it is claimed that the official method for potash salts gives too high results owing to impure precipitates. The reports of results of cooperating chemists are as follows: E. L. Baker, Geneva, N. Y.: Moist filter paper pulp was used in one of each set of duplicates and a thick pad of asbestos in the other, with no appreciable variation in results. In some cases the precipitate showed a tendency to run through the filter paper pulp. It was easier, however, to wash the filter paper free from acid. Corrections were made for a blank of 0.3 cc of potassium hydroxid. Corrections were also made for blanks in the official method. You will notice that in the case of the mixed fertilizer the two methods differ by about 0.4 of a per cent. During a series of determinations I was unable to obtain any closer agreement. E. C. Carlyle, College Station, Tex.: The use of pulped filter paper for filtering the phosphomolybdate is found satisfactory and it reduces the bumping when the liquid is heated for the purpose of dissolving the potash salt. G. S. Farnham, Cincinnati, Ohio: I regret to report that I failed to get checks for the volumetric method. P. Rudnick, Chicago, Ill.: It seems from the results by the official method that there is some truth in the claim that the method for mixed fertilizers when applied to sulphate of potash gives somewhat lower results. The proposed volumetric method |