Grain-Size Analysis of Soil (Including Both Mechanical and Hydrometer Analyses) - Soil Properties: Testing, Measurement, and Evaluation - page 126

6. For the sieve analysis of the fine aggregates, compute the total per-
centage that passed each sieve by subtracting the summation of the
mass retained on this and all previous sieves from the mass of the
oven-dried sample for hydrometer analysis, dividing this difference
by the calculated mass of the total oven-dried hydrometer analysis
sample (i.e., M from step 5), and multiplying the quotient by 100.
The summation of the mass retained on this and all previous sieves
begins with the No. 10 sieve, which retains no soil during the fine
aggregate sieving (because the sample for hydrometer analysis con-
sists only of soil that previously passed the No. 10 sieve); however,
the mass of the oven-dried sample for hydrometer analysis is the
mass passing the No. 10 sieve.
7. Recall that the data recorded in the hydrometer analysis consist of
hydrometer readings and corresponding readings of temperature of
the suspension for specified elapsed times. The first step in the
computational procedure is to apply the composite correction to each
hydrometer reading. (It will be recalled that for a given application,
this correction will be a function of temperature.) Denote the
corrected hydrometer reading R for later use. The percentage of soil
remaining in suspension (i.e., percent of soil finer, or P ) at each level
at which the hydrometer measured the density of the suspension
may be calculated using one of the following equations [1]
For hydrometer 151H:

100,000 M

G

c 1

> 2

P R G 1 (10-1)

d1 2

G G 1

For hydrometer 152H:

Ra
M 100

P (10-2)

where:
P percentage of soil remaining in suspension at level at
which hydrometer measures density of suspension
M mass of total oven-dried hydrometer analysis sample (see
step 5)
G specific gravity of soil particles
G 1 specific gravity of liquid in which soil particles are sus-
pended; use numerical value of one in both instances in
equation (in the first instance, any possible variation
produces no significant effect, and in the second, the
composite correction for R is based on a value of one for G 1 )
R hydrometer reading with composite correction applied
a correction factor to be applied to reading of hydrometer
152H. (Values shown on the scale are computed using a
specific gravity of 2.65; correction factors can be obtained
from Table 10-2.)