Determination of cation exchange capacity of forest soil by ammonium acetate exchange method (2)

Five, pre-treatment

(1) Soil moisture content

Determine the soil moisture content in accordance with the "Gravimetric Method for the Determination of Soil Dry Matter and Moisture" (HJ613-2001),

(2) Treatment process of acid and neutral soil samples

Weigh 2.

Add first-grade deionized water to the soil-carrying centrifuge tube several times, wash into the distillation flask, control the volume of the washed water to be 50-80mL, and add 2mL liquid paraffin and 1g magnesium oxide for distillation

(3) Treatment process of calcareous soil samples

Weigh 2.

(4) Blank sample

For each batch of samples to be analyzed, prepare a blank sample according to the above-mentioned sample processing procedure

Six, analysis and testing

Titrate the distillate with 0.

Seven, calculation and presentation of results

The soil cation exchange capacity is expressed in CFC (cmol/kg) and calculated according to the formula (1) for drying soil weight:

In the formula, C——concentration of hydrochloric acid standard solution, mol/L;

V——Consumption volume of hydrochloric acid standard solution, mL;

V ₀ ——Consumption volume of blank reagent hydrochloric acid standard solution, mL;

m——The quality of the windy soil;

wH ₂ O-- moisture content of air-dried soil

8.

The allowable deviation for the determination of soil cation exchange capacity, when the measured value is above 30cmol/kg, the absolute deviation should not be greater than 5%; when the value is 10-30cmol/kg, the absolute deviation should be 0.

Nine, matters needing attention

(1) In the process of repeatedly treating the soil with ammonium acetate solution and ethanol , sufficient shaking can effectively reduce the number of treatments

(2) In the process of centrifuging the soil sample and discarding the supernatant and transferring the soil sample, the loss of the soil sample should be avoided as much as possible

Related Links: Determination of Cation Exchange Capacity of Forest Soil Ammonium Acetate Exchange Method (1)