By means of the absorptive power of soils the farmer, if he puts on an excess of potash or phosphoric acid as a fertilizer, does not lose it but is able to reap some benefits from it in the next and even in succeeding crops. If it were not for this power the best method for applying fertilizers would be a much more complicated problem than it is at present; and it would be necessary to apply them at just the proper season and in nicely regulated amounts to insure against loss. =132. Method of Determining Absorption of Chemical Salts.=—The soil which is to be used for this experiment should be treated as has been indicated and passed through a sieve the meshes of which do not exceed half a millimeter in size. From twenty-five to fifty grams of the fine earth may be used for each experiment. The fine earth should be placed in a flask with 100 to 200 cubic centimeters of the one-tenth to one-hundredth normal solution of the substance to be absorbed. The flask should be well shaken and allowed to stand with frequent shaking twenty-four to forty-eight hours at ordinary temperatures. The whole is then to be thrown upon a folded filter and an aliquot part of the filtrate taken for the estimation. The methods of determining the quantities of the substances used will be found in other parts of this manual. It is recommended to conduct a blank experiment with water under the same conditions in order to determine the amount of the material under consideration abstracted from the soil by the water alone. The difference in the strength of the solution as filtered from the soil, corrected by the amount indicated by the blank experiment, and the original solution will give the absorptive power of the soil for the particular substance under consideration. If it should be desired to determine the absorptive power of the soil for all the ordinary chemical fertilizing materials at the same time, a larger quantity of the sample should be taken corresponding to the increased amount of the standard solutions used. About 500 cubic centimeters of the mixed salt solution should be shaken with 125 grams of the earth and the process carried on in general as indicated above. The absorption coefficient of an earth for any given salt according to Fesca,[96] is the quantity of the absorbed material expressed in milligrams calculated to a unit of 100 grams of the soil. =133. Method of Pillitz and Zalomanoff.=—It is recommended by Pillitz and Zalomanoff[25] to reject the old method, _viz._, shaking the soil with the solution in a flask, and substitute the filtration method both because it gives a more natural process and because the results are more constant. The apparatus is shown in Fig. 15. [Illustration: FIGURE 15. ZALOMANOFF’S APPARATUS FOR DETERMINING ABSORPTION OF SALTS BY SOILS. ]