Atech Center - Hydrometer Procedure

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Calculations

Step III. Express Percentage of Soil in Suspension
as Part of Total Sample Mass

% of Total Mass =

P X (100 - % Retained on 2mm Sieve)/100

where:

W = mass of air dried soil

W₁ = mass of oven dried soil

Example: 42% of sample material was retained on the 2mm (#10) sieve. P is 37.6.

% of Total Mass = 37.6 X (100 - 42/100)

% of Total Mass = 37.6 X (58/100)

% of Total Mass = 37.6 X (0.58)

% of Total Mass = 21.8

Step IV. Determine Diameters of Particles of Soil in Suspension

where:

L = Effective depth of hydrometer (derived from Table 2)

T = Interval of time from beginning of test

K = Constant based on test temperature and material specific gravity (derived from Table 3)