Abstract

In order to evaluate the accuracy of various settling tubes in use, experiments were conducted using settling tubes having 5, 7.6, 12.8, and 30.5 cm diameters, 80 and 140 cm. settling lengths, sphere sizes of .02 to .03, .295 to .35, and 0.83 to 0.99 mm. diameter, and sample sizes from 0.05 to 4 gms. The experiments showed 7.6 cm. (3 in.) diameter settling tubes produced inaccuracies up to 34%, 12.8 cm (5 in.) diameter tubes produced inaccuracies less than 8%, and 3.05 cm (12 in.) diameter tubes produced inaccuracies less than 3%. A settling tube 13 to 16 cm. in diameter, having a settling length of 140 cm., and utilizing coarse sediment (.3 to 2 mm) samples weighing 1 to 2 gms or fine sediment (.02 to .5 mm) samples weighing 0.6 gm. are recommended for particle-size analyses utilizing settling tubes.

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