The solutions should be approximately tenth normal, the actual strength in each case being determined by analysis. The phosphorus is determined as magnesium pyrophosphate in the usual way, the potash as potassium platinochlorid, the ammonia by collecting the distillate from soda in half normal hydrochloric acid and titrating with standard alkali, and the nitrate by Warington’s modification of Schlösing’s method for gas analysis. The details of these methods of determination will be given later. One hundred grams of the sifted, air-dried soil are placed in a rubber stopped bottle and treated with 250 cubic centimeters of the solution to be tested. The digestion is continued for forty-eight hours in each case, the bottles being thoroughly shaken at the end of twenty-four hours. At the end of the treatment the solutions are filtered and the salts determined in aliquot portions. The details of this method are essentially those already described. =137. Statement of Results.=—Duplicate analyses should be made and the tabulation of the data is illustrated in the following analyses by Huston: Na₂HPO₄ cubic Weight of Weight of P₂O₅ Salt centimeters Mg₂P₂O₇ in Mg₂P₂O₇ in absorbed removed filtrate taken. twenty-five filtrate. by 100 per cubic grams cent. centimeters of soil. the solution. (a) 25 0.1368 gram 0.0962 gram (b) 25 0.0963 „ 0.2589 29.6 gram —————— Mean 0.0963 „ KCl cubic Weight of Weight of K₂O Salt centimeters K₂PtCl₆ in K₂PtCl₆. absorbed removed filtrate taken. twenty-five by 100 per cubic grams cent. centimeters of soil. solution. (a) 25 0.6154 gram 0.4505 gram (b) 25 0.4540 „ 0.3161 26.5 gram —————— Mean 0.4523 „