Hydrometer particle-size distribution

Figure 21. Hydrometer tests to determine particle size distribution in a suspension and the same suspension after dispersion of the particle floes or aggregates. The difference in the two curves is an indication of the degree of dispersion or degree of flocculation or aggregation.

Hydrometer Grain size distribution of silt and clay size particles ... 

The gradation curve of the material passing through the 0.075 mm sieve, that is, the particle size distribution, is determined from the hydrometer readings according to Stock s law. Details for determining the particles diameter can be found in ASTM D 422 (2007) or AASHTO T 88 (2013). 

Chain Hydrometer. A type of hydrometer that is operated at constant depth by a chain loading device similar to that used on some analytical balances. It has been used for the determination of the particle-size distribution of clays. Chain Silicates. See silicate... 

Particle size distribution Sieve analysis Sedimentation test, Hydrometer test Only if coarse fraction present 1,2, 3,4... 

DIVER METHOD- This is a modification of the hydrometer method. Variation in effective density i and hence concn, is measured by totally immersed divers. These are small glass vessels of approximately streamline shape, ballasted to be in stable equilibrium, with the axis vertical, and to have a known density slightly greater than that of the sedimentation liq. As the particles settle, the diver moves downwards in hydrodynamic equilibrium at the appropriate density level. The diver indicates the position of a weight concn equal to the density difference between the diver and the sedimentation liq. Several divers of various densities are required, since each gives only one point on the size distribution curve... 

In gravity settling the sample is dispersed in a liquid and then allowed to settle in a sedimentation cell. The height of the particles in the cell is then measured, or the specific gravity of the dispersing liquid is measured at different time intervals, which gives an indication of the size distribution. The hydrometer, or Bouyoucos, method is frequently used to classify the amount of sand, silt, and clay in soils. 

The accuracy of the hydrometer method for particle-size measurement is obviously dependent upon some mean distance along its bulb which is taken as a reference point. Along the entire submerged stem and bulb the density of the concentration and the size-distribution of particles are constantly changing. Their reference point may be determined as follows Let L be the distance from the surface of the suspension to the volume center of the hydrometer then if the submerged part of the stem is neglected... 

Schweyer (1942) compared various methods of particle-size measurement (except centrifuging). He found excellent agreement between pipette and hydrometer methods. He considers the former the best method for determining the particle-m/.c distribution of sub-sieve material by sedimentation, and prefers the hydrometer as a rapid control procedure. 

In liquid sedimentation methods, a sample of catalyst powder is dispersed in a liquid and the changes in concentration of solid (i.e., changes in density) at a selected height in the column of liquid are determined as a function of time for example, by means of a plummet suspended from one arm of an analytical balance or by the use of a hydrometer (176). The coarse particles settle more rapidly, and it is possible to calculate the size distribution from the observed data, taking into account the density of the liquid and the density of the particles with the pores full of liquid. 

Soil classification particle grain size distribution, hydrometer, Atterberg limits, field identification tests, linear shrinkage and moisture content test ... 

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