However, these two authors rightly call attention to the fact that plant roots absorb their nutrition from the soil solution. For this reason the sodium chloride content of the solution must be examined, and in each sample the amount of soil moisture must also be determined. Soil samples for the determination of sodium chloride content are placed in closed containers at the collecting places. The determination of moisture (see p. 213) should be performed as soon as possible. Then 50 g. of soil are dried, and the determination of chlorine is made in the usual manner by leaching out the chlorides with distilled water and titrating the dissolved chlorides with accurately standardized silver nitrate, with potassium chromate as indicator. (Braun-Blanquet 1932:200)
BRAUN-BLANQUET, Josias. 1932. Plant sociology: the study of plant communities. (Trans.: George D. Fuller; Henry S. Conard) New York: McGraw-Hill Book Company.