AgricuNwal Chemistry.
407
section of the cell, the percentage of the current passing through the diaphragm depends on the surface, thickness, and nature of the diaphragm, on the nature of the electrolyte, and on the fall of potential in the electrolyte. T h e current will always pass through an interposed plate unless prevented by polarization. Copper is deposited upon the negative side of a platinum partition even when the drop of potential in the electrolyte from one side of the partition to the other is less than that theoretically required to deposit copper from a normal copper sulphate solution. The author does not see why this should be so. T h e explanation is that the energy absorbed is that theoretically necessary, but part of the copper deposited is redissolved. giving back energy, and so only a fraction of the critical voltage is necessary to supply all J. W. RICHARDS. the energy required.
AGRICULTURAL CHEnISTRY. Influence of the Soil on the Protein Content of Crops, BY A. R. WHITSON, F. J. WELLS,AND A. VIVIAN. Wis. Agr. Expt. Sta. Rep., 1902, pp. 1g2--20g.-In a study of this question, plant-house and field experiments were conducted with corn, oats, barley, rape, and cow-peas. T h e crops were grown on soils of different degrees of fertility and determinations were made at frequent intervals of the available nitrogen in the soils and the protein in the crops. I n one test, the proteid nitrogen, in oats grown on soils having the same physical composition but different degrees of richness in nitrates, was 1.93 per cent. on the poorest soil, 2.53 per cent. on the medium fertile soil, and 2.66 per cent. on the richest soil. I n a similar test with corn the figures were, respectively, 1.35, 1-59, and 1.80 per cent. T h e results of the experiments as a whole indicate that farm crops vary greatly in their protein content a t the same stage of development, and that this variation may exist even when the crops are making practically equal growth. Under similar seasonal conditions, the amount of nitrates in the soil is believed to be the most important factor in causing this variation. H. W. LAWSON. Field Experiments with Fertilizers. BYC. S. PHELPS.Conn. Storrs Agr. Ex@. Sta. Rep., 1901, pp. 122-147.-0ne object of these experiments, which are continued from year to year, was to study the effect of nitrogenous fertilizers upon the amount of protein in the crops grown. I n the case of corn, the percentages of nitrogen and protein in both grain and stover were highest where the largest quantity of nitrogen had been used in the fertilizer. I n the leguminous plants (cow-peas and soy-beans) the protein was increased but little, if any, by the use of nitrogenous fertilizers. H. UT. LAWSON. Pot Experiments with Nitrogenous Fertilizers. BY C. S. PHELPS. Conn. Storrs Agr. Exjt. Sta. Rep., 1901, pp. 154-164.
408
Review of American Chemical Reseavch.
-The object of these experiments was the same as that noted in the field experiments above. T h e results for three years indicate that the percentages of nitrogen and protein in some of the conimoil grasses and in millet were greatly increased by the nitrogen applied in the fertilizers. While the experiment with oats \vas not as satisfactory, similar results were obtained. On the other hand, the protein in so!..beans was not increased by the use of fertilizers rich iri nitrogen. H. W. LAWSON.
A Rotation Study. BY F.S. SHIVER.S. C. Agr. Expf. Sta. Bull. No. 7 9 , 62 pp. -Two series of twelve tenth-acre plats each were used in this study. I n one series, commercial fertilizers were applied and cow-peas when grown were removed. In the other series no fertilizers were applied, but cow-peas were frequently grown and plowed under. Various rotations were compared. T h e soil and subsoil of each series were analyzed at the beginning of the study and again at the close, three !.ears later. Available phosphoric acid was determined by digestion with ammonium citrate solution and with one-fifth normal hydrochloric acid. Available potash was determined by digestion with one-fifth normal calcium chloride solution and with alkaline ammonium chloride. Each crop grown was analyzed. T h e available phosphoric acid was invariably higher by the ammonium citrate method, attributed to this solvent dissolving some of the phosphoric acid in combination with humus. As regards the availability of phosphoric acid i n the soil, the results with the animonium citrate method agreed approximately with crop records i n 50 per cent. of the cases and the results with hydrochloric acid agreed i n 66 per cent. T h e results with the two methods for determining available potash agreed closely and corresponded to crop data i n 63 per cent, of the cases. T h e author believes that none of these methods, in their present shape, give absolutely reliable results for available phosphoric acid and potash. Cotton grown continuously on some of the plats greatly reduced the percentage of humus. S o better results as regards the niaiiitenarice of h u m u s in the soils were obtained by plowing under cow-peas than by t h e removal of this crop combined with the use of cottonseed meal, acid phosphate, and kainit as fertilizers. Wheat was grown on all the plats the fourth year, the yields in 13 out of z-+ cases agreeing closely with the gains and losses of nitrogen, humus, a n d humic nitrogen in the plats as previously observed. H. \V. Lawsox. Nitrification in Different Soils. BY W. X. WITHERSAND G. S.FRAPS.N: C. Agr. Expt. S t a . Rep., 1902, pp. 31-41.T h e rate of nitrification of ammonium sulphate and cottonseed meal in 8 soils from 4 different states was studied. Calclum carbonate was found to exert a decided accelerating influence upon the nitrification of both substances, especially the ammonium sul-
Agriculiural Chemistry.
409
phate. Ammonium sulphate was nitrified to a greater extent than cottonseed meal in some soils, while in other soils the reverse was true. Some of the soils showed very little nitrifying power. Brief notes are given on the nitrifying organisms.
H. W. LAWSON. The Determination of Sulphur and Chlorine in Plants. BY G. S. FRAPS. N. C. Agr. Expt. Sta, Rep., 1902,pp. 44-49.This work was presented in greater detail before the Association of Official Agricultural Chemists, in 1902. T h e results as summarized favor the nitric acid method, modified by the substitution of calcium acetate for potassium nitrate, for the determination of total sulphur, and the method of ignition with sodium carbonate for the determination of chlorine. T h e loss of chlorine which takes place on ignition isconsidered as due probably to the decomposition of chlorides and not to their volatilization, H. W. LAWSON. The Sulphur Content of Some Vegetable Materials. BY W. A. WITHERS AND G. S.FRAPS.N. C. Agr. Expt. Sta. Rep., 1902, pp. 53-58.-The authors determined the sulphur in a number of vegetable materials, using the nitric acid method modified by the use of calcium acetate in place of one-half of the potassium nitrate. Some of the average results are as follows : Cottonseed meal 1.10per cent. (sulphur as SO,). cottonseed hulls 0.176 per cent., oats 0.491 per cent., cow-peas 0.466per cent., corn 0.338 per cent., and peanuts 0,471per cent. T h e ash contained from 'i6, to '/, of the total amount of sulphur found in these plants. T h e conclusion is drawn, therefore, that the sulphur content of an ash is no indication as to the amount of sulphur in the plant. T h e sulphur content was greater in some cases than that of potash, soda, lime, or magnesia, making it seem probable to the authors that sulphur plays a more important part in plant nutrition than has been suspected. H. W. Lawsoh..
Ash Analyses of Some New [lexico Plants. BY A. Goss. New Mex. Agr. Expt. Sta. Bull. No. 4 4 , 14 pp. -The author reports in tabular form ash analyses of salt grass. bunch grass, sea blite, cachanilla, shadscale, creosote bush, popotillo, century plant, sotol, soapweed, Spanish dagger, ocotillo, prickly pear, tree cactus, chico bush, and alfalfa, and describes the different plants. I n general, the percentage of ash was high as compared with that of plants in nonarid regions. The percentage in the water-free material varied from 3.44in the case of cachanilla to 24.18in one species of prickly pear. Not only the total ash, but the different constituents varied greatly with the different species of plants. There was no uniformity in the ash constituents of plants grown o n alkali soils. T h e kind of plant has apparently as much to do with its mineral composition as has the environment under which it grew. T h e value of the nitrogen, potash, and phosphoric acid
410
Review of American Chemical Research.
removed from the soil by alfalfa was estimated at current eastern prices to exceed $1 i per ton of dried material. T h e author made a comparative study of the sulphur in the ash, as determined by the method of the Association of Official Agricultural Chemists, and the sulphur in the unburned plant material, as determined by fusion with potash and potassium nitrate. Averaging all results, the sulphur in the ash was 0.29 per cent., and the sulphur in t h e plant 0.71 per cent. T h e percentage of sulphur lost i n burning varied from 34 to 94 per cent., with different plants. T h e conclusion is therefore drawn that the determination of sulphur in t h e ash with a view to determining the amount originally present i n the plant is absolutely worthless. I n determining sulphur in the plant material, the author finally resorted to the use of large iron crucibles instead of platinum as previously given in this method . H . Vi'. L~wsor;. On the Digestibility and Availability of Food Materials. BY Catt72. sforrs Agr. Expt. Sta. Rep.. 1901,pp. I 79-2pj.-Fifty digestion experiments made with three men are reported. T h e diet was simple, containing a number of common animal and vegetable food materials. T h e digestibilit!, of t h e nutrients was apparently unaffected by the amount of mriscular exercise taken. T h e results of these and other experinieiits, while not warranting final conclusions, indicate that the coefficients of availability (commonly called digestibility) of the nutrients of a mixed diet, when eaten by people in good health, are iiot far from 92 per cent. for protein, 9 j per cent. for fat, and 97 per ceiit. for carbohydrates. T h e proportioils of animal and vegetable foods modify these factors, however, to a coiisiderable extent. Roughly speaking, about g j to 96 per ceiit. of the total organic matter i n a mixed diet and 91 to 92 per ceiit. of the total energy will be H. UT.LAWSOS. available.
rv. 0. ATWATER.
Dietary Studies in American Cities. Edited by I
