Haineng Instrument: Determination method of soil cation exchange amount (cation exchange amount measuring instrument)-华强电子网

Experimental principle

in accordance with"

LYT 1243-1999 Determination of cation exchange capacity in forest soils. The soil was repeatedly treated with a 1 mol/L ammonium acetate solution to make the soil an ammonium ion saturated soil, and excess ammonium acetate was washed away with 95% ethanol, and then magnesium oxide was added for distillation. The distilled ammonia is absorbed by a boric acid solution, and is determined by standard acid droplets, and the amount of soil cation exchange is calculated based on the amount of ammonium ions .

Instruments and reagents

K1160 automatic Kjeldahl analyzer (cation exchange meter)

Analytical balance (one in ten thousand)

Centrifuge

100ml centrifuge tube)

Reagent configuration reference

LYT 1243-1999 Determination of cation exchange capacity in forest soils.

experiment procedure

1) Ion exchange

Weighing through

2g of air-dried soil sample of 1mm sieve hole, put into a 100ml centrifuge tube and add a small amount of 1mol/L ammonium acetate solution along the wall, stir the soil sample with rubber head glass to make it into a uniform mud state, and then

Add ammonium acetate solution to the total volume

60 ml, and stir well, then wash the rubber rod with ammonium acetate solution, and the solution is taken into the centrifuge tube.

The centrifuge tube was made up to a mass balance with ammonium acetate solution and coarsely balanced. Balanced centrifuge tubes are placed symmetrically into the centrifuge and centrifuged

3-5min, the speed is 3000r/min.

The supernatant after each centrifugation is collected in

In a 250 ml volumetric flask, treat with ammonium acetate solution 2-3 times until no calcium ions react in the leaching solution.

(Check calcium ion: take leachate

5ml, placed in a test tube, add 1ml of pH10 buffer solution, and then add a little KB indicator, such as blue, indicating no calcium ions: such as purple, indicating calcium ions). Finally, the volume was adjusted with ammonium acetate solution, and the supernatant was retained for the determination of the exchangeable salt base.

2) repeated cleaning

Add a small amount to the centrifuge tube

95% ethanol, stir the soil with a rubber glass rod, so that

It becomes a mud state, and then add ethanol to about

60ml, stir well with a rubber glass rod to wash away the excess ammonium acetate on the surface of the soil, and there must be no small earth mass.

Then centrifuge the tube with ethanol to make it mass balance, coarsely level, and put it into the centrifuge symmetrically, centrifuge

3-5 min, the speed is 3000r/min, and the ethanol solution is discarded. Repeat this 2-3 times with ethanol until the last time the ethanol solution has no ammonium ions (check the ammonium ion: take the ethanol solution, immediately add a drop of Nessler's reagent, if there is no yellow, it means no ammonium ion, can also use A Base red-bromocresol green mixed indicator for inspection).

3) On-machine test

After washing away the excess ammonium ions, rinse the outer wall of the centrifuge tube with water, add a small amount of water to the centrifuge tube, stir into a paste, then wash the slurry into the digestive tube with water, and scrub the inner wall of the centrifuge tube with a rubber glass rod. All soil samples are transferred to the digestive tract, and the volume of washed water should be controlled.

50-80ml.

2 ml of liquid paraffin and 1 g of magnesium oxide were added to the digestive tract.

Immediately put the digestive tube on the instrument

, the setup procedure is as follows:

Each soil sample was tested in parallel for not less than two times. At the same time, do a blank test.

4) Instrument output The instrument automatically titrates and gives the content of cation exchange. The built-in calculation formula of the instrument is as follows:

In the middle

:CEC: cation exchange amount, cmol(+)/kg;

C:

The concentration of the hydrochloric acid standard solution,

Mol/L ;

V:

The amount of hydrochloric acid standard solution,

mL ;

V ₀ :

Blank test hydrochloric acid standard solution

, mL ;

m ₁ :

Air-dried soil sample quality,

g ;

K ₂ :

Conversion of air-dried soil into conversion factor of dried soil

;

10:

will

The mmol is converted to a multiple of cmol.