# Presentation: 128346

## Particle-Size Distribution

**Settled Sand**

**Settled Silt**

**Clay left in **
**Suspension**

**Soil Mineral Particles Settled in Cylinder**

**	****Remember Stokes Law: The bigger they are, the faster they fall!**

**Laboratory Analysis**

## Particle-Size Distribution (continued)

**Specific Gravity: The weight of a substance relative to the weight of an equal volume of water.**

- This hydrometer reading is 1.000

**Laboratory Analysis**

## Particle-Size Distribution (continued)

- 100mL Dispersing Solution
- 50mL Distilled H2O
- Put all three into a 500mL beaker and stir for one minute.
- Cover with plastic wrap and let mixture sit for 24 hours.
- Remove plastic wrap and stir for one minute.
- Measure the distance from base of 500mL cylinder (0mL line) to 500mL line.
- Pour entire soil mixture into 500mL cylinder.
- Fill to 475mL line with distilled H2O and add to 500mL line with distilled H2O from squirt bottle.
- Cover cylinder with plastic wrap.

**Laboratory Analysis**

**Particle-Size Distribution (continued)**

## Particle-Size Distribution (continued)

- From when you start timing:

- Time	Action
- 1 min. 30 sec. 	Put Hydrometer in cylinder.
- 2 min. 	Read hydrometer (remove, rinse and dry hydrometer).
- 2 min. 30 secs.	Put thermometer in cylinder.
- 3 min. 30 secs. 	Take temperature reading (take out, clean and dry thermometer).
- 11 min. 30 sec. 	Put Hydrometer in cylinder.
- 12 min. 	Read hydrometer (remove, rinse and dry hydrometer).
- 12 min. 30 secs. 	Put thermometer in cylinder.
- 13 min. 30 secs. 	Take temperature reading (take out, clean and dry thermometer).

- Sample Time
- (10:06 30 secs.)
- (10:07)
- (10:07 30 secs.)
- (10:08 30 secs.)
- (10:16 30 secs.)
- (10:17)
- (10:17 30 secs.)
- (10:18 30 secs.)

- Start timing. (e.g. timing starts at 10:05 am)

**Laboratory Analysis**

**Particle-Size Distribution (continued)**

## Particle-Size Distribution (continued)

- 2. Weigh 25 g of dried, sieved soil and pour it into a 250 mL or larger beaker.  Add 100 mL of the dispersing solution and about 50 mL of distilled water to the beaker.  Stir vigorously with a spoon or sitrring rod for at least one minute.  Be sure the soil is thoroughly mixed and does not stick to the bottom of the beaker.  Do not let any of the soil suspension spill out the top.

**Laboratory Analysis**

**Particle-Size Distribution (continued)**

## Particle-Size Distribution (continued)

- 4. Measure the distance between the 500 mL mark and the base of the cylinder.  (You can place the measuring stick inside the cylinder to get this measurement.).

- 5. Read the temperature at which your hydrometer has been calibrated (such as 15.6° C [60° F] or 20° C) which is found on the body of the hydrometer.

- Record both the distance and the temperature on the Particle-Size Distribution Data Work Sheet.

- Temperature
- Calibration

**Laboratory Analysis**

**Particle-Size Distribution (continued)**

## Particle-Size Distribution (continued)

- 7. Add enough water to fill the cylinder to the 500 mL mark.

- 8. Securely cover the top of the cylinder using plastic wrap or other secure cover.

- 9. Mix vigorously by rotating the covered sylinder hand-over-hand at least 10 times.  Be sure the soil is thoroughly mixed in the solution and does not stick to the bottom of the cylinder.  Try not to let any of the suspension leak out the top.

- 500 mL mark

**Laboratory Analysis**

**Particle-Size Distribution (continued)**

## Particle-Size Distribution (continued)

- 11. After 1 minute, carefully lower the hydrometer into the cylinder so it floats in the suspension.  Steady the hydrometer to keep it from bobbing up and down.

- 12. At exactly **2 minutes **after the cylinder was set down, read the line on the hydrometer that is closest to the surface of the soil suspension and record your result on the Particle-Size Distribution Data Work Sheet.

- 13.	Remove the hydrometer, rinse it, dry it, and gently put it down in a safe place.

**(Sample starting time)**

**Laboratory Analysis**

**Particle-Size Distribution (continued)**

## Particle-Size Distribution (continued)

- This hydrometer reading is: 1.008

**Laboratory Analysis**

**Particle-Size Distribution (continued)**

## Particle-Size Distribution (continued)

- 15.	Take another hydrometer reading in the undisturbed cylinder at **12 minutes**.  Place the hydrometer carefully in the suspension about 30 seconds before making the reading to allow it to settle.

- 16.	Take and record another temperature reading for the suspension.

- 17.	Rinse the hydrometer and thermometer off when they have been removed from the suspension and dry them.

- 18.	Record these results on the Particle-Size Distribution Data Work Sheet.

**Laboratory Analysis**

**Particle-Size Distribution (continued)**

## Particle-Size Distribution (continued)

- 19. Leave the cylinder undisturbed for 24 hours (or until the beginning of the same class period the next day).

- 21. Discard the soil suspension by pouring it into a special pail and spill the contents outside in a place for discarding soil materials.  **Do not pour the suspension down the sink! **

- 22.	Carefully rinse and dry the hydrometer, thermometer, beakers, and cylinders, and repeat the above steps two more times for the same horizon so that you have a total of three sets of results for each sample.

- 23. Repeat this procedure for each soil sample from every horizon.

**Laboratory Analysis**

**Particle-Size Distribution (continued)**