FIRST DAY. MONDAY-AFTERNOON SESSION. No report on phosphoric acid was presented because of the death, during the year, of W. J. Jones, jr., the referee. THE EFFECT OF MASS AND DEGREE OF FINENESS ON THE By H. D. HASKINS (Agricultural Experiment Station, Amherst, Mass.). The purpose of this paper is to bring before the association the results of some studies made at the Massachusetts Agricultural Experiment Station on a high grade precipitated phosphate, which tend to show that the present official method for the determination of available phosphoric acid in fertilizers is not applicable to this class of materials. The precipitated phosphate which served for the studies is prepared by treating the phosphoric acid obtained in the manufacture of glue with hydrated or slaked lime. The product is very finely divided, white, neutral in reaction, said to be dried at 150°F., and nearly chemically pure bicalcium phosphate. The scope of the experiment was to study the effect of a 1- and 2-gram charge, using an ammonium citrate solution made neutral to cochineal as indicator (official) and ammonium citrate solution made neutral to TABLE 1. Analyses of precipitated phosphate material ground to pass a 1 mm. sieve. per cent per cent per cent 29.70 per cent per cent 4.49 42.92 31.01 11.91 39.60 3.32 per cent per cent per cent per cent 11.91 123 NUMBER OF SAMPLE TABLE 2. Analyses of precipitated phosphate material ground to pass a 100 mesh sieve. *Two hundred mesh sieve; 1 gram charge. litmus solution as indicator; also, to study the effect of the two solutions on the product ground to pass a 100 mesh sieve. Unusual care was taken in standardizing the solutions of neutral citrate of ammonia. Considerable difference exists in the two solutions standardized by the two indicators, cochineal and litmus. The results obtained by the two solutions did not seem to be constant in all cases, a somewhat higher available phosphoric acid having been obtained by the citrate solution, standardized with litmus, in all cases where a 2-gram charge was employed. On the other hand, the citrate solution, standardized with cochineal, gave invariably higher results with a 1gram charge, irrespective of the degree of fineness of the phosphate. The available phosphoric acid obtained by both solutions was appreciably higher when used on the phosphate ground to pass a 100 mesh sieve. Finer grinding did not increase the availability of the phosphoric acid to any great extent. The most striking results obtained in the study are noticed in the very much higher yield of available phosphoric acid in all cases where a 1-gram charge was used. This would indicate that in a product containing such a large proportion of available phosphoric acid (nearly 40 per cent) a 2-gram charge produces a highly saturated citrate solution, resulting in a correspondingly low phosphoric acid availability. It is believed that the subject is of sufficient importance to warrant recognition by the association. It is recommended RECOMMENDATION. That the referee on phosphoric acid for 1918 be instructed to make a study of the analysis of precipitated phosphate with a view to modifying the present official method, or to substituting therefor some suitable method for the estimation of available phosphoric acid in this class of materials. E. O. Thomas (Paul-Gale-Greenwood Building, Norfolk, Va.), presented a paper giving some results obtained for "Insoluble Phosphoric Acid in Organic Base Goods"1, using the official method2. No report was presented by the committee on basic slag, to cooperate with the committee on vegetation tests on the availability of phosphoric acid in basic slag. REPORT ON NITROGEN. By H. D. HASKINS (Agricultural Experiment Station, Amherst, Mass.), Collaborators were asked to study the West Coast refraction method for the analysis of nitrate of soda and the use of sodium sulphate in place of potassium sulphate in the Gunning method. No samples were submitted but each collaborator was requested to use samples from his own collection. Determination of nitrogen in nitrate of soda by the Ulsch-Street, zinc iron, modified Kjeldahl and the ferrous sulphate-zincsoda methods in addition to the West Coast refraction method was requested. WEST COAST REFRACTION METHOD. Moisture. Weigh approximately 10 grams of the material (60 mesh) accurately, spread out on a tared watch glass and dry in a hot air oven at 160°C. for exactly 5 hours; cool in a desiccator and weigh. The loss in weight represents moisture. Insoluble residue.-Dissolve approximately 50 grams of the material in 200-300 cc. of hot water and filter, preferably on a weighed Gooch crucible. Make the filtrate up to 1000 cc. and preserve it for the subsequent determinations of the other impurities. Dry the crucible and contents at 120-130°C. to constant weight. The net weight represents the total insoluble matter. Sodium chlorid.-Titrate 100 cc. of the solution, equivalent to 5 grams of material, with N/10 silver nitrate solution. Before beginning the titration add 1-2 mg. of sodium carbonate to sharpen the end point with the potassium chromate indicator, (1 cc. of a saturated potassium chromate solution). The silver nitrate solution must be added slowly so that the red precipitate of silver chromate disappears as fast as it is formed; otherwise, there is danger of its being occluded in the silver chlorid. The end point is taken at the first permanent reddish tint. One cc. of N/10 silver nitrate equals 0.005846 gram of sodium chlorid. The report should read: "Total chlorids equivalent to per cent of NaCl". 1 J. Ind. Eng. Chem., 1917, 9: 865. 2 Assoc. Official Agr. Chemists, Methods, 1916, 4. Sodium sulphate.-In the determination of sulphates use exactly 100 cc. of the filtrate from the insoluble residue determination. Expel nitric acid by evaporation with an excess of hydrochloric acid. Precipitate the sulphuric acid with 10 cc. of 10% barium chlorid solution. Barium sulphate multiplied by 0.60859 equals sodium sulphate. The result should be stated in terms of sodium sulphate. Potassium oxid.-Determine the percentage of potassium oxid according to the official method, reporting the results as "Potash equivalent to potassium nitrate". It was estimated that the time required for the determination of the impurities in the case of the West Coast method was at least three times more than for the direct nitrogen determination by any one of the other methods. It does not seem to your referee that the method has sufficient merit to warrant further study, especially as the association has two official and one tentative method for the analysis of nitrate salts. SUBSTITUTION OF SODIUM SULPHATE FOR POTASSIUM SULPHATE IN THE GUNNING METHOD. Four collaborators have reported results on these methods and quite a variety of substances of difficult oxidation were included in the work. |