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U <br />• <br />MECHANICAL ANALYSIS AND TEXTURAL CLASSIFICATION <br />(Revised Bouyoucs Methods) <br />1. Weigh 50 g of a fine textured, 100 g of coarse textured <br />(Sand) material and place in a French square bottle. Fill <br />the bottle 2/3 full with distilled water and add 25 ml of <br />1 N sodium hexametaphosphate (100.2 g/liter) <br />2. Place bottle on shaker at 120 excursions per minute for 16 hrs. <br />3. Transfer to the special cylinder and fill to the lower mark <br />with distilled water while the hydrometer is in suspension. <br />(If 100 gms of soil are used, fill to the upper mark), <br />4. Remove hydrometer and shake suspension vigorously. Place <br />cylinder on desk and record the time. At the end of 20 <br />seconds, carefully insert the hydrometer and read the <br />hydrometer at the end of 40 seconds. Record the reading <br />on the data sheet. <br />5. Remove the hydrometer from the suspension. Record the <br />temperature reading on the data sheet.. <br />6. For each degree above 67°F, add 0.2 to the reading to get <br />th~ corrected hydrometer reading. For each degree less than <br />67 F, subtract 0.2 from the reading. <br />7. Calculate the percent sand in the sample. <br />The hydrometer is calibrated so that the corrected reading <br />gives the grams of soil material in suspension. The sand <br />settles to the bottom of the cylinder within 90 seconds, <br />therefore, the 40 second hydrometer reading actually <br />gives the amount of silt and clay in suspension. The <br />weight of sand in the sample is obtained by subtracting <br />the corrected hydrometer reading from the total weight of the <br />sample. The percentage sand is calculated by dividing the weight <br />of the sand by the weight of the sample and multiplying by 100. <br />8. Take a reading at the end of two hours. Insert hydrometer <br />just before the two-hour reading is made. <br />9. Calculate the percent clay in the sample. <br />At the end of tsao hours, the silt in addition to the sand <br />has settled out of suspension. The corrected hydrometer <br />reading at the end of tcoo hours represents the grams of <br />clay in the sample. <br /> <br />10. Calculate the percent of silt in the sample. <br />Find the percent silt by difference. Subtract the sum of the <br />percentage of sand and cla•~ from 100 to get the percent silt. <br />6-1.08 <br />