ASTM D422-63(2007)e2 pdf free.Standard Test Method for Particle-Size Analysis of Soils.
ASTM D422 covers the quantitative determination of the distribution of particle sizes in soils. The distribution of particle sizes larger than 75 μm (retained on the No. 200 sieve) is determined by sieving, while the distribution of particle sizes smaller than 75 μm is determined by a sedimentation process, using a hydrometer to secure the necessary data (Note 1 and Note 2).
7. Determination of Composite Correction for Hydrometer Reading
7.1 Equations for percentages of soil remaining in suspension, as given in 14.3, are based on the use of distilled or dcmineralizcd water. A dispersing agent is used in the water, however, and the specific gravity of the resulting liquid is appreciably greater than that of distilled or demincralized water.
7.1.1 Both soil hydrometers are calibrated at 68°F (20°C), and variations in temperature from this standard temperature produce inaccuracies in the actual hydrometer readings. The amount of (he inaccuracy increases as the variation from the standard temperature increases.
7.1.2 Hydrometers are graduated by the manufacturer to be read at the botom of the meniscus formed by the liquid on the stem. Since it is not possible to secure readings of soil suspensions at the bottom of the meniscus. readings must be taken at the top and a correction applied.
7.1.3 The net amount of the corrections for the three items enumerated is designated as the composite correction, and may he determined experimentally.
7.2 For convenience, a graph or table of composite corrections for a series of 10 temperature differences for the range of expected test temperatures may be prepared and used as needed. Measurement of the composite corrections may he made at two temperatures spanning the range of expected test temperatures. and corrections for the intermediate temperatures calculated assuming a straight-line relationship between the two observed values.
7.3 Prepare 1000 rnL of liquid composed of distilled or demineralized water and dispersing agent in the same proporlion as will prevail in the sedimentation (hydrometer) test. Place the liquid in a sedimentation cylinder and the cylinder in the constant-temperature water bath, set for one of Lhe two temperatures to be used. When the temperature of the liquid becomes constant, insert the hydrometer. and, after a short interval to permit the hydrometer to come to the temperature of the liquid, read the hydrometer at the top of the meniscus formed on the stem. For hydrometer 151 H the composite correction is the difference between this reading and one; for hydrometer 152H it is the difference between the reading and zero. Bring the liquid and the hydrometer to the other temperature to be used, and secure the composite correction as before.ASTM D422-63(2007) pdf free download.