of Testing and Materials (1968). The suspended particles were decanted, 
ovendried for 24 hours at 100° Celsius, ground fine with a porcelain mortar 
and pestle, and analyzed for size distribution by the American Society of 
Testing and Materials (1968) method performed for the other mineral solids. 
This particular size distribution of Si0) particles is referred to in this 
report as less than 15 micrometers SiO». 
The natural sediments collected from the Patuxent River were analyzed 
by a slightly modified procedure from the above method. Preliminary work 
showed that this material was approximately 75- to 80-percent salt and 
water by weight. Appropriate triplicate volumes of this natural material 
were removed from the holding tanks. These volumes were calculated to 
contain between 5 and 10 grams of dry solids (inorganic). Also, these 
volumes were corrected upward for the amount (weight) of organic matter 
present. These quantities of solids were placed into large Pyrex beakers 
(1-liter capacity) and an appropriate amount of 30 percent hydrogen 
peroxide (H202) was added to each beaker. The amount (volume) of H 09 
(30 percent) needed to oxidize the organic matter present in the sediment 
was found to be a volume which would produce a final concentration of 
H202 in the sediment volume of approximately 5 percent. The oxidation 
reaction was quite violent initially. The reaction was allowed to proceed 
overnight in a hood with air bubbling slowly through the sediment-H 209 
mixture to remove the excess H 90>. 
When gas evolution had ceased the following day, 750 milliliters of 
deionized glass-distilled water were added to each beaker. The sediment 
was resuspended by stirring with a glass rod and allowed to settle. The 
supernatant was carefully decanted and another 750 milliliters of deionized 
glass-distilled water rinse were added to each beaker. 
A 0.2-milliliter sample of supernatant water was then taken from each 
beaker and the dissolved ion concentration of each solution was determined 
with the freezing-point depression osmometer normally used in our hematolo- 
gical analyses. Salt concentration was read from a standard curve relat- 
ing freezing-point depression and osmolal concentration to sodium chloride 
(NaCl) concentration in milligram kilogram™! water. If the salt concen- 
tration was greater than 300 milligrams NaCl kilogram! water, the suspen- 
sion was allowed to settle, the clear supernatant was decanted, and an 
additional rinse of 750-milliliter deionized distilled water was added 
to each beaker. The sediment was resuspended and allowed to settle. The 
clear supernatant was decanted and the beaker containing the washed sedi- 
ment made up to 500 milliliters with fresh, deionized glass-distilled 
water was placed into an ultrasonic bath (45 kilohertz) for 30 minutes. 
Then, the suspension was placed into a glass cylinder, made up to volume 
with deionized distilled water, and the analysis followed as described in 
American Society of Testing and Materials (1968), except that the dis- 
persing agent, sodium pyrophosphate (NayP207), was not added. 
Values are reported as percent by weight remaining in suspension 
(percent finer than) plotting against equivalent spherical diameters 
according to Stokes' law. 
30 
