First, reagents and instruments
l.0.5N sodium oxysulfide (chemically pure) solution, 0.5N sodium oxalate (chemically pure) solution, 0.5N sodium hexametaphosphate (chemically pure)
Solution, these three solutions are chosen for different soil pH values.
2. Isoamyl alcohol (chemically pure)
3.2% sodium carbonate (chemically pure) solution.
4. Soft water, prepared by adding 200 ml of sodium sodium carbonate to 1500 ml of tap water, and letting it stand overnight, after clearing, the upper supernatant is soft water, and the amount of 2% sodium carbonate increases with the hardening degree of tap water. .
l. A type of hydrometer (ie, Oil Quality hydrometer); scale range 0-60, minimum scale unit 1.O g / liter, should be corrected before use.
2. Washing sieve, small copper sieve with a pore diameter of 0.1 mm and a sieve diameter of 5 cm.
3. Soil sieve: pore size is 3.1, O.5, O.25 mm.
4. Stir bar, glass rod with rubber head.
5. Settling cylinder (1000 ml) measuring cylinder (100 ml), triangular flask (500 ml), funnel (diameter 7 cm, 4 cm), washing bottle, ordinary beaker, dropper, etc.
6. Electric heating plate, clock, thermometer (±0.1C), oven (5-200 ° C), balance (inductive volume 0.0001 g and 0.Ol grams), aluminum box and so on.
Second, the operation steps:
1. Weighing: Weigh 50 g of air-dried soil sample (accurate to 0.01 g) through a 1 mm sieve hole, place it in a 500 ml Erlenmeyer flask, and add distilled water or soft water to wet the sample, otherwise called 10 g (accurate to 0.0001) The soil sample was placed in an aluminum box, baked in an oven (l05 ° C) to constant weight (about 6 hours), cooled and weighed to calculate the moisture content and dry soil weight.
2. Sample dispersion: calcareous soil (50 g sample) plus 60 ml of O.5N sodium hexametaphosphate, neutral soil (50 g sample) plus 0.5 N sodium oxalate 20 ml, acidic soil (50 g sample) plus 0.5 N 40 ml of sodium hydroxide, then, the physical dispersion treatment of the sample by the usual boiling method, that is, in the 500 ml triangle bottle containing the dispersing agent, and then adding distilled water or soft water, so that the volume of the soil in the flask is about 250 ml, cover the bucket, shake the triangle bottle, then put it on the hot plate and heat it to boil. Before boiling, the triangle bottle should be shaken frequently to prevent the soil sedimentation bottle from forming a hard block or charring. After boiling, keep boiling for 1 hour. .
3. Prepare the suspension: Place a small copper sieve with a mesh diameter of 0.1 mm on the bucket, rest on the l000 ml settling drum, pass the cooled flask to the 0.1 mm sieve, and lighten with a rubberized glass rod. Gently wash the granules on the sieve and rinse them with distilled or soft water until all the soil particles <0.1 mm enter the settling tank, and leave the clear liquid under the sieve, but the amount of the suspension washed into the settling tank should not exceed 1000 ml.
Move >0.1 ml of gravel sand left on the small copper sieve into the lead box, pour the upper supernatant, dry the scale and calculate the percentage, and sieve with 1,0.5,0.25 mm aperture, 3-1,1-0.5 0.5-0.25, 0.25-0.1 mm gravel or grit were weighed separately and the percentages were calculated.
The settling cylinder containing the soil liquid is made up to 1000 ml with distilled water or soft water, placed on a flat table with a small temperature change, arranged neatly, numbered into the record sheet, and prepared for the hydrometer Petroleum Density Meter, stopwatch (or alarm clock), Thermometer (±0.1 °C), etc.
4. Determine the specific gravity of the suspension: Place the settling tube containing the suspension on a stable test table with small changes in day and night temperature, measure the temperature of the suspension, stir the suspension with a stir bar for 1 minute (about 30 times each), and record the start time. According to the relationship between the temperature time and the particle size listed in Table 1-l, according to the measured liquid temperature and the maximum diameter value of the particle size to be tested, the time for measuring the specific gravity is selected, and the hydrometer is gently put into the suspension in advance. In the selected time, the hydrometer reading is measured. After the necessary correction is made, the cumulative content of the particles smaller than the selected millimeter is represented. According to the above steps, <0.05, <0.01, respectively. <100mm and other specific gravity of the soil particles reading.
5. Result calculation
1 Convert the air-dried soil sample to the dry sample weight:
2 necessary correction for the hydrometer reading
Correction value = dispersant correction value + temperature correction value
Where: a, dispersant correction value = number of milliliters added to the dispersant × equivalent concentration of the dispersant × dispersant milliequivalent weight (mg) × l0-3 (g / l)
b. Check the temperature correction value in Table 1-2.
Corrected reading = original reading – corrected value
5 Subtracting the percentage of soil particle content of two adjacent particle sizes, that is, the percentage of the grain size of the two particle size ranges.